Re-enable C++/CLI test coverage previously gated on VS 2026 toolset availability

[Copilot]

VS 2026 Helix scout queues were failing C++/CLI coverage because tests were broadly disabled behind a temporary skip tied to missing VC tooling. This change removes those temporary disables so the C++/CLI scenarios execute again now that the image/tooling issue has been addressed.

• Re-enable Build test suite C++/CLI coverage

  • Removed Skip from all FullMSBuildOnlyFact tests in:
    • GivenThatWeWantToBuildACppCliProject
    • GivenThatWeWantToBuildACppCliProjectWithTransitiveDeps
    • SourceLinkTests.Cpp

• Re-enable Pack C++/CLI coverage

  • Removed Skip from GivenThatWeWantToPackACppCliProject.It_cannot_pack_the_cppcliproject.

• Re-enable Publish C++/CLI coverage

  • Removed Skip from GivenThatWeWantToPublishACppCliProject.When_referenced_by_csharp_project_it_publishes_and_runs.

• Change shape

  • No product/runtime behavior changes.
  • Test logic and assertions are unchanged; only test gating metadata was updated.

// Before
[FullMSBuildOnlyFact(Skip = "https://github.com/dotnet/sdk/issues/53789")]

// After
[FullMSBuildOnlyFact]

[marcpopMSFT]

These were disabled in main and servicing, then reenabled in main, then codeflow disabled them again. Let's try reenabling.

[Copilot]

Pull request overview

Re-enables previously skipped C++/CLI test coverage across Build/Pack/Publish test suites by removing temporary Skip metadata that was added due to missing VC toolset availability on VS 2026 Helix scout images.

Changes:

• Removed Skip = "https://github.com/dotnet/sdk/issues/53789" from FullMSBuildOnlyFact-gated C++/CLI Build tests.
• Removed the same Skip from the C++/CLI Pack and Publish coverage tests.
• Re-enabled the C++-related SourceLink test by removing the temporary skip.

Reviewed changes

Copilot reviewed 5 out of 5 changed files in this pull request and generated no comments.

Show a summary per file

File	Description
test/Microsoft.NET.Publish.Tests/GivenThatWeWantToPublishACppCliProject.cs	Removes temporary skip to re-enable the C++/CLI publish scenario test.
test/Microsoft.NET.Pack.Tests/GivenThatWeWantToPackACppCliProject.cs	Removes temporary skip to re-enable the C++/CLI pack scenario test.
test/Microsoft.NET.Build.Tests/SourceLinkTests.cs	Removes temporary skip to re-enable the C++ SourceLink test.
test/Microsoft.NET.Build.Tests/GivenThatWeWantToBuildACppCliProjectWithTransitiveDeps.cs	Removes temporary skips to re-enable transitive-deps C++/CLI build validations.
test/Microsoft.NET.Build.Tests/GivenThatWeWantToBuildACppCliProject.cs	Removes temporary skips to re-enable core C++/CLI build coverage scenarios.