Consolidate Razor compiler code into a single DLL

[jjonescz]

Merge the following DLLs into one (Microsoft.CodeAnalysis.Razor.Compiler):

• Microsoft.AspNetCore.Razor.Language (move into folder Language)
• Microsoft.CodeAnalysis.Razor (move into folder CSharp)
• Microsoft.NET.Sdk.Razor.SourceGenerators (move into folder SourceGenerators)
• Microsoft.AspNetCore.Mvc.Razor.Extensions (move into folder Mvc)

Merge tests into one project, as well (Microsoft.CodeAnalysis.Razor.Compiler.Tests).

Roadmap:

• [x] Transport Microsoft.AspNetCore.Mvc.Razor.Extensions v1 and v2 into SDK and make rzc.dll tool use them.
  • [x] https://github.com/dotnet/razor/pull/9266
  • [x] https://github.com/dotnet/sdk/pull/35273
  • [x] https://github.com/dotnet/sdk/pull/35371
• [x] https://github.com/dotnet/razor/pull/9129 to see whether anything breaks
  • [x] https://github.com/dotnet/sdk/pull/34928
  • [x] https://github.com/dotnet/sdk/pull/36059
  • [x] https://github.com/dotnet/sdk/pull/36041
  • [x] https://github.com/dotnet/aspnetcore/pull/50369
  • [x] in Roslyn: https://github.com/dotnet/roslyn/pull/69655
  • [x] https://github.com/dotnet/roslyn/pull/70485
  • [x] No longer needed as we removed the IVTs: https://github.com/dotnet/roslyn/issues/71024
    • [x] When IVTs are fixed in Roslyn, re-enable host outputs in Razor. https://github.com/dotnet/razor/pull/9447
    • [x] Clean this up after merging of DLLs into one is complete.
• [x] ~Fixup runtime compilation which lives in aspnetcore.~ Runtime compilation is fixed to v6.0 of Razor.
• [x] Fixup roslyn, aspnetcore, and sdk repos when the update flows there (and again when the updated aspnetcore flows back into sdk), for example:
  • https://github.com/dotnet/roslyn/blob/3630eb1758c131d0f359704a0e8cc874e109d269/src/VisualStudio/Core/Test/ProjectSystemShim/VisualStudioProjectTests/AnalyzerReferenceTests.vb#L212
  • https://github.com/dotnet/aspnetcore/blob/0684c8aa38c6b9926bae3d901741a83c453dc413/eng/Dependencies.props#L16
  • https://github.com/dotnet/sdk/blob/cfa6ec2353784e22171bc4539181a1a935e066e9/src/Tests/Microsoft.NET.Sdk.Razor.Tests/ScopedCssIntegrationTests.cs#L93
• [x] Redo https://github.com/dotnet/razor/pull/8471 and when complete, redo the steps above - renaming the intermediate assemblies to the final one.

Old plan:

- [x] https://github.com/dotnet/razor/pull/8386 - [x] https://github.com/dotnet/razor/pull/8395 - [x] https://github.com/dotnet/razor/pull/8471 - [ ] Update VSIX on Roslyn side similarly to https://github.com/dotnet/roslyn/pull/67501 - [ ] Update transports. - [ ] Update runtime compilation in aspnetcore. - [ ] Delete the old packages.

To allow servicing of the old compiler (branch `release/dev17.6`): Not needed, I think, since we have shims now (#8941)

- [ ] https://github.com/dotnet/razor/pull/8594 - [ ] Take dependency on the old compiler in the main branch. > **Note** To service the old compiler: update the 17.6 branch, release new version of this old package, update main branch to consume that version of the old package, build and insert into VS.

See also:

• https://github.com/dotnet/razor/issues/8399

[jaredpar]

Integration tests are blocked on https://github.com/dotnet/dnceng/issues/563