Cleanup versions a bit

[dougbu]

This is about following up on e133683 as discussed starting at #21567 (comment).

• Remove the Internal.AspNetCore.Analyzers project and all references to it
  • We no longer have pub-ternal types outside analyzers and tools. Therefore, we don't need to warn about them anymore.
  • Remove $(DisablePubternalApiCheck) settings too
• Move from Yarn.MSBuild 1.15.2 to 1.22.4
  • This version is mentioned in both global.json and eng/Tools.props. The versions should match between those files.
• Update AddContent target in Microsoft.AspNetCore.AzureAppServices.SiteExtension.csproj to set 5.0 package versions based on the projects
  • Remove the redundant @(PackageReference)s for the 5.0 packages earlier in the project file
  • Move comments about changing how these references are handled down into the AddContent target and call out the need to do this when switching to net6.0
• Move the MsQuicPackage.* versions from QuicSampleClient and QuicSampleApp projects to eng/Versions.props

[Pilchie]

@dougbu Should we move this to rc2?

[dougbu]

@pranavkm fixed the first bullet with #24693 and I fixed the third bullet with #25406. Both changes are in RC1 and I'd forgotten to check them off here.

Agree the remainder should happen in RC2.

[Pilchie]

Is this GA or 6.0 now?

[dougbu]

What remains is just cleanup and the existing bits work. So, 6.0.