Ensure UserSecretsIdAttribute is added to assembly (#63415)

When Microsoft.Extensions.Configuration.UserSecrets is referenced transitively, for example through Extensions.Hosting, the UserSecretsIdAttribute isn't getting added to the built assembly. This is because the logic is contained in a `build` folder which is excluded by the dependency from Extensions.Hosting.

The fix is to move the logic to `buildTransitive`, so it gets picked up by NuGet. One wrinkle is that the logic now conflicts with the netstandard compatibility logic added by the library infrastructure. In order to make progress, disable that logic for this package and rely on its dependencies to raise the compat error.

Contributes to #63246

Author: eerhardt

src/libraries/Microsoft.Extensions.Configuration.UserSecrets/src/Microsoft.Extensions.Configuration.UserSecrets.csproj

@@ -7,6 +7,13 @@
     <DisableImplicitAssemblyReferences>false</DisableImplicitAssemblyReferences>
     <IsPackable>true</IsPackable>
     <PackageDescription>User secrets configuration provider implementation for Microsoft.Extensions.Configuration.</PackageDescription>
+
+    <!--
+      See https://github.com/dotnet/runtime/issues/63413.
+      Since this library contains its own buildTransitive logic, disable the netstandard compat logic since they conflict.
+     -->
+    <DisableNETStandardCompatErrorForNETCoreApp>true</DisableNETStandardCompatErrorForNETCoreApp>
+    <DisableNETStandardCompatErrorForNETFramework>true</DisableNETStandardCompatErrorForNETFramework>
   </PropertyGroup>
 
   <ItemGroup>
@@ -17,8 +24,8 @@
   </ItemGroup>
 
   <ItemGroup>
-    <Content Include="build\netstandard2.0\$(MSBuildProjectName).props" PackagePath="%(Identity)" />
-    <Content Include="build\netstandard2.0\$(MSBuildProjectName).targets" PackagePath="%(Identity)" />
+    <Content Include="buildTransitive\netstandard2.0\$(MSBuildProjectName).props" PackagePath="%(Identity)" />
+    <Content Include="buildTransitive\netstandard2.0\$(MSBuildProjectName).targets" PackagePath="%(Identity)" />
   </ItemGroup>
 
 </Project>