Make a number of RenderNode constants vars

This updates some of the properties in the RenderNode tree to be mutable. A number of the top-level properties in RenderNode are already mutable, and making these additional properties mutable as well allows callers to modify these values.

rdar://164748009

Sources/SwiftDocC/Model/Rendering/Content/RenderBlockContent.swift

@@ -630,7 +630,7 @@ public enum RenderBlockContent: Equatable {
         /// A list of rendering block elements.
         public typealias Cell = [RenderBlockContent]
         /// The list of row cells.
-        public let cells: [Cell]
+        public var cells: [Cell]
 
         /// Creates a new table row.
         /// - Parameter cells: The list of row cells to use.
@@ -692,18 +692,18 @@ public enum RenderBlockContent: Equatable {
         /// A term rendered as content.
         public struct Term: Codable, Equatable {
             /// The term content.
-            public let inlineContent: [RenderInlineContent]
+            public var inlineContent: [RenderInlineContent]
         }
         /// A definition rendered as a list of block-content elements.
         public struct Definition: Codable, Equatable {
             /// The definition content.
-            public let content: [RenderBlockContent]
+            public var content: [RenderBlockContent]
         }
 
         /// The term in the term-list item.
-        public let term: Term
+        public var term: Term
         /// The definition in the term-list item.
-        public let definition: Definition
+        public var definition: Definition
     }
 
     /// A row in a grid-based layout system that describes a collection of columns.
@@ -713,18 +713,18 @@ public enum RenderBlockContent: Equatable {
         /// This may be different then the count of ``columns`` array. For example, there may be
         /// individual columns that span multiple columns (specified with the column's
         /// ``Column/size`` property) or the row could be not fully filled with columns.
-        public let numberOfColumns: Int
+        public var numberOfColumns: Int
 
         /// The columns that should be rendered in this row.
-        public let columns: [Column]
+        public var columns: [Column]
 
         /// A column with a row in a grid-based layout system.
         public struct Column: Codable, Equatable {
             /// The number of columns in the parent row this column should span.
-            public let size: Int
+            public var size: Int
 
             /// The content that should be rendered in this column.
-            public let content: [RenderBlockContent]
+            public var content: [RenderBlockContent]
         }
     }
 
@@ -734,21 +734,21 @@ public enum RenderBlockContent: Equatable {
     /// license, or copyright text.
     public struct Small: Codable, Equatable {
         /// The inline content that should be rendered.
-        public let inlineContent: [RenderInlineContent]
+        public var inlineContent: [RenderInlineContent]
     }
 
     /// A collection of content that should be rendered in a tab-based layout.
     public struct TabNavigator: Codable, Equatable {
         /// The tabs that make up this tab navigator.
-        public let tabs: [Tab]
+        public var tabs: [Tab]
 
         /// A titled tab inside a tab-based layout container.
         public struct Tab: Codable, Equatable {
             /// The title that should be used to identify this tab.
-            public let title: String
+            public var title: String
 
             /// The content that should be rendered in this tab.
-            public let content: [RenderBlockContent]
+            public var content: [RenderBlockContent]
         }
     }
 
@@ -770,10 +770,10 @@ public enum RenderBlockContent: Equatable {
         }
 
         /// The style that should be used when rendering the link items.
-        public let style: Style
+        public var style: Style
 
         /// The topic render references for the pages that should be rendered in this links block.
-        public let items: [String]
+        public var items: [String]
 
         /// Create a new links block with the given style and topic render references.
         public init(style: RenderBlockContent.Links.Style, items: [String]) {
@@ -785,10 +785,10 @@ public enum RenderBlockContent: Equatable {
     /// A video with an optional caption.
     public struct Video: Codable, Equatable {
         /// A reference to the video media that should be rendered in this block.
-        public let identifier: RenderReferenceIdentifier
+        public var identifier: RenderReferenceIdentifier
 
         /// Any metadata associated with this video, like a caption.
-        public let metadata: RenderContentMetadata?
+        public var metadata: RenderContentMetadata?
 
         /// Create a new video with the given identifier and metadata.
         public init(identifier: RenderReferenceIdentifier, metadata: RenderContentMetadata? = nil) {

Sources/SwiftDocC/Model/Rendering/RenderNode.Tag.swift

@@ -16,7 +16,7 @@ public extension RenderNode {
         /// The tag type.
         let type: String
         /// The text to display.
-        let text: String
+        var text: String
 
         /// A pre-defined SPI tag.
         static let spi = Tag(type: "spi", text: "SPI")

Sources/SwiftDocC/Model/Rendering/Symbol/AttributesRenderSection.swift

@@ -14,9 +14,9 @@ import Foundation
 public struct AttributesRenderSection: RenderSection, Equatable {
     public var kind: RenderSectionKind = .attributes
     /// The section title.
-    public let title: String
+    public var title: String
     /// The list of attributes in this section.
-    public let attributes: [RenderAttribute]?
+    public var attributes: [RenderAttribute]?
 
     /// Creates a new attributes section.
     /// - Parameter title: The section title.

Sources/SwiftDocC/Model/Rendering/Symbol/ConformanceSection.swift

@@ -37,7 +37,7 @@ public struct ConformanceSection: Codable, Equatable {
     var conformancePrefix: [RenderInlineContent] = [.text("Conforms when")]
 
     /// The section constraints rendered as inline content.
-    let constraints: [RenderInlineContent]
+    var constraints: [RenderInlineContent]
 
     /// Additional parameters to consider when rendering conformance constraints.
     struct ConstraintRenderOptions {

Sources/SwiftDocC/Model/Rendering/Symbol/ParameterRenderSection.swift

@@ -12,7 +12,7 @@
 public struct ParametersRenderSection: RenderSection, Equatable {
     public var kind: RenderSectionKind = .parameters
     /// The list of parameter sub-sections.
-    public let parameters: [ParameterRenderSection]
+    public var parameters: [ParameterRenderSection]
 
     /// Creates a new parameters section with the given list.
     public init(parameters: [ParameterRenderSection]) {

Sources/SwiftDocC/Model/Rendering/Symbol/PossibleValuesRenderSection.swift

@@ -24,14 +24,14 @@ public struct PossibleValuesRenderSection: RenderSection, Equatable {
         /// The value name.
         let name: String
         /// Details content, if any.
-        let content: [RenderBlockContent]?
+        var content: [RenderBlockContent]?
     }
 
     public var kind: RenderSectionKind = .possibleValues
     /// The title for the section, `nil` by default.
-    public let title: String?
+    public var title: String?
     /// The list of named values.
-    public let values: [NamedValue]
+    public var values: [NamedValue]
 
     /// Creates a new possible values section.
     /// - Parameter title: The section title.

Sources/SwiftDocC/Model/Rendering/Symbol/PropertiesRenderSection.swift

@@ -16,9 +16,9 @@ import Foundation
 public struct PropertiesRenderSection: RenderSection {
     public var kind: RenderSectionKind = .properties
     /// The title for this section.
-    public let title: String
+    public var title: String
     /// The list of properties.
-    public let items: [RenderProperty]
+    public var items: [RenderProperty]
 
     /// Creates a new property-list section.
     /// - Parameters:
@@ -60,9 +60,9 @@ public struct RenderProperty: Codable, TextIndexing, Equatable {
     /// The list of possible type declarations for the property's value including additional details, if available.
     public let typeDetails: [TypeDetails]?
     /// Additional details about the property, if available.
-    public let content: [RenderBlockContent]?
+    public var content: [RenderBlockContent]?
     /// Additional list of attributes, if any.
-    public let attributes: [RenderAttribute]?
+    public var attributes: [RenderAttribute]?
     /// A mime-type associated with the property, if applicable.
     public let mimeType: String?
     /// If true, the property is required in its containing context.

Sources/SwiftDocC/Model/Rendering/Symbol/RESTBodyRenderSection.swift

@@ -14,7 +14,7 @@ import Foundation
 public struct RESTBodyRenderSection: RenderSection, Equatable {
     public var kind: RenderSectionKind = .restBody
     /// A title for the section.
-    public let title: String
+    public var title: String
 
     /// Content encoding MIME type for the request body.
     public let mimeType: String
@@ -23,14 +23,14 @@ public struct RESTBodyRenderSection: RenderSection, Equatable {
     public let bodyContentType: [DeclarationRenderSection.Token]
 
     /// Details about the request body, if available.
-    public let content: [RenderBlockContent]?
+    public var content: [RenderBlockContent]?
 
     /// A list of request parameters, if applicable.
     ///
     /// If the body content is `multipart/form-data` encoded, it contains a list
     /// of parameters. Each of these parameters is a ``RESTParameter``
     /// and it has its own value-content encoding, name, type, and description.
-    public let parameters: [RenderProperty]?
+    public var parameters: [RenderProperty]?
 
     /// Creates a new REST body section.
     /// - Parameters:

Sources/SwiftDocC/Model/Rendering/Symbol/RESTEndpointRenderSection.swift

@@ -50,7 +50,7 @@ public struct RESTEndpointRenderSection: RenderSection, Equatable {
     }
 
     /// The title for the section.
-    public let title: String
+    public var title: String
 
     /// The list of tokens.
     public let tokens: [Token]

Sources/SwiftDocC/Model/Rendering/Symbol/RESTParametersRenderSection.swift

@@ -29,9 +29,9 @@ public enum RESTParameterSource: String, Codable {
 public struct RESTParametersRenderSection: RenderSection, Equatable {
     public var kind: RenderSectionKind = .restParameters
     /// The title for the section.
-    public let title: String
+    public var title: String
     /// The list of REST parameters.
-    public let parameters: [RenderProperty]
+    public var parameters: [RenderProperty]
     /// The kind of listed parameters.
     public let source: RESTParameterSource
 

Sources/SwiftDocC/Model/Rendering/Symbol/RESTResponseRenderSection.swift

@@ -14,9 +14,9 @@ import Foundation
 public struct RESTResponseRenderSection: RenderSection, Equatable {
     public var kind: RenderSectionKind = .restResponses
     /// The title for the section.
-    public let title: String
+    public var title: String
     /// The list of possible REST responses.
-    public let responses: [RESTResponse]
+    public var responses: [RESTResponse]
 
     enum CodingKeys: String, CodingKey {
         case kind
@@ -70,7 +70,7 @@ public struct RESTResponse: Codable, TextIndexing, Equatable {
     /// A type declaration of the response's content.
     public let type: [DeclarationRenderSection.Token]
     /// Response details, if any.
-    public let content: [RenderBlockContent]?
+    public var content: [RenderBlockContent]?
 
     /// Creates a new REST response section.
     /// - Parameters:

Sources/SwiftDocC/Model/Rendering/Symbol/TaskGroupRenderSection.swift

@@ -13,9 +13,9 @@ public struct TaskGroupRenderSection: RenderSection, Equatable {
     public let kind: RenderSectionKind = .taskGroup
 
     /// An optional title for the section.
-    public let title: String?
+    public var title: String?
     /// An optional abstract summary for the section.
-    public let abstract: [RenderInlineContent]?
+    public var abstract: [RenderInlineContent]?
     /// An optional discussion for the section.
     public var discussion: (any RenderSection)? {
         get {