Remove ambiguity by removing this overload

[davidfowl]

Follow up on #7826 (comment). After a discussion with @eerhardt, we're removing this api

[Copilot]

PR Overview

This PR removes an ambiguous overload by requiring callers to use ReferenceExpression.Create when creating connection strings. Key changes include:

• Removal of the test case “ConnectionStringResourceWithInterpolated” that used the ambiguous overload.
• Updating all connection string creation calls to use ReferenceExpression.Create across tests and sample projects.
• Removal of the overloaded method in ConnectionStringBuilderExtensions.cs that accepted an interpolated string handler.

Reviewed Changes

File	Description
tests/Aspire.Hosting.Tests/WithReferenceTests.cs	Removed overloaded test for interpolated connection string usage.
tests/Aspire.Hosting.Tests/AddParameterTests.cs	Updated connection string creation to use ReferenceExpression.Create.
tests/Aspire.Hosting.Tests/WaitForTests.cs	Updated connection string creation to use ReferenceExpression.Create.
playground/ParameterEndToEnd/ParameterEndToEnd.AppHost/Program.cs	Updated connection string creation to use ReferenceExpression.Create.
tests/TestingAppHost1/TestingAppHost1.AppHost/Program.cs	Updated connection string creation to use ReferenceExpression.Create.
src/Aspire.Hosting/ConnectionStringBuilderExtensions.cs	Removed the overload accepting an interpolated string, cleaning up the API.

Copilot reviewed 6 out of 6 changed files in this pull request and generated no comments.

Comments suppressed due to low confidence (2)

tests/Aspire.Hosting.Tests/WithReferenceTests/WithReferenceTests.cs:270

• The removal of the 'ConnectionStringResourceWithInterpolated' test means the previous API behavior is no longer validated. Ensure that tests sufficiently cover the new usage with ReferenceExpression.Create.

[Fact] public async Task ConnectionStringResourceWithInterpolated() { ... }

src/Aspire.Hosting/ConnectionStringBuilderExtensions.cs:52

• Verify that any documentation or internal references to the removed overload are updated so that users are aware that only ReferenceExpression.Create is supported.

/// Removed overload for AddConnectionString using ExpressionInterpolatedStringHandler.

[eerhardt]

Thanks! LGTM