[msbuild/tests] Use 'dotnet test' for the MSBuild tests.

[rolfbjarne]

This is another step towards removing Mono.

This required a few changes:

• Nullability updates in test code.
• Explicitly sorted list of strings in a warning message, to make the warning text stable.
• Stopped merging system assemblies in the merged tasks assembly. This was necessary for to solve a problem with duplicate types:
  • The netstandard2.0 version of System.Reflection.Metadata.dll contains
    the UnconditionalSuppressMessageAttribute type (internally).
  • Since we ILMerge the tasks assembly, this type ends up in
    Xamarin.iOS.Tasks.dll (internally).
  • The test assembly can't be a net472 assembly, because that means using
    the netfx/desktop versions of the Microsoft.Build.* assemblies, which
    don't work on .NET (they check for Mono, but .NET isn't Mono, so the
    check fails and a PlatformNotSupportedException is thrown).
  • So I bumped the test assembly to be a net8.0 assembly, but then there's
    a conflict between the UnconditionalSuppressMessageAttribute shipped
    in .NET vs the one in Xamarin.iOS.Tasks.dll (because the test assembly
    can see the internals of Xamarin.iOS.Tasks.dll).
  • The fix that seems to work is to not merge system assemblies in the
    Xamarin.iOS.Tasks.dll assembly. Xamarin.iOS.Tasks.Windows.dll
    already does this, so hopefully there are no problems on Windows, and on
    macOS our tests doesn't reveal any problems.

[vs-mobiletools-engineering-service2]

📚 [CI Build] Artifacts 📚

Artifacts were not provided.

Pipeline on Agent
Hash: [PR build]

[vs-mobiletools-engineering-service2]

✅ API diff for current PR / commit

NET (empty diffs)

• iOS: (empty diff detected)
• tvOS: (empty diff detected)
• MacCatalyst: (empty diff detected)
• macOS: (empty diff detected)

✅ API diff vs stable

.NET (No breaking changes)

• iOS: vsdrops gist (No breaking changes)
• tvOS: vsdrops gist (No breaking changes)
• MacCatalyst: vsdrops gist (No breaking changes)
• macOS: vsdrops gist (No breaking changes)

ℹ️ Generator diff

Generator Diff: vsdrops (html) vsdrops (raw diff) gist (raw diff) - Please review changes)

Pipeline on Agent
Hash: 61256976e1939a617f739692c2e112cb33bc922d [PR build]

[vs-mobiletools-engineering-service2]

💻 [CI Build] Tests on macOS X64 - Mac Sonoma (14) passed 💻

✅ All tests on macOS X64 - Mac Sonoma (14) passed.

Pipeline on Agent
Hash: 61256976e1939a617f739692c2e112cb33bc922d [PR build]

[vs-mobiletools-engineering-service2]

💻 [CI Build] Tests on macOS M1 - Mac Big Sur (11) passed 💻

✅ All tests on macOS M1 - Mac Big Sur (11) passed.

Pipeline on Agent
Hash: 61256976e1939a617f739692c2e112cb33bc922d [PR build]

[vs-mobiletools-engineering-service2]

💻 [CI Build] Tests on macOS M1 - Mac Monterey (12) passed 💻

✅ All tests on macOS M1 - Mac Monterey (12) passed.

Pipeline on Agent
Hash: 61256976e1939a617f739692c2e112cb33bc922d [PR build]

[vs-mobiletools-engineering-service2]

💻 [CI Build] Tests on macOS M1 - Mac Ventura (13) passed 💻

✅ All tests on macOS M1 - Mac Ventura (13) passed.

Pipeline on Agent
Hash: 61256976e1939a617f739692c2e112cb33bc922d [PR build]

[vs-mobiletools-engineering-service2]

🚀 [CI Build] Test results 🚀

Test results

✅ All tests passed on VSTS: test results.

🎉 All 97 tests passed 🎉

Tests counts

✅ cecil: All 1 tests passed. Html Report (VSDrops) Download
✅ dotnettests (iOS): All 1 tests passed. Html Report (VSDrops) Download
✅ dotnettests (MacCatalyst): All 1 tests passed. Html Report (VSDrops) Download
✅ dotnettests (macOS): All 1 tests passed. Html Report (VSDrops) Download
✅ dotnettests (Multiple platforms): All 1 tests passed. Html Report (VSDrops) Download
✅ dotnettests (tvOS): All 1 tests passed. Html Report (VSDrops) Download
✅ framework: All 2 tests passed. Html Report (VSDrops) Download
✅ fsharp: All 4 tests passed. Html Report (VSDrops) Download
✅ generator: All 1 tests passed. Html Report (VSDrops) Download
✅ interdependent-binding-projects: All 4 tests passed. Html Report (VSDrops) Download
✅ introspection: All 4 tests passed. Html Report (VSDrops) Download
✅ linker: All 40 tests passed. Html Report (VSDrops) Download
✅ monotouch (iOS): All 7 tests passed. Html Report (VSDrops) Download
✅ monotouch (MacCatalyst): All 7 tests passed. Html Report (VSDrops) Download
✅ monotouch (macOS): All 8 tests passed. Html Report (VSDrops) Download
✅ monotouch (tvOS): All 7 tests passed. Html Report (VSDrops) Download
✅ msbuild: All 2 tests passed. Html Report (VSDrops) Download
✅ xcframework: All 4 tests passed. Html Report (VSDrops) Download
✅ xtro: All 1 tests passed. Html Report (VSDrops) Download

Pipeline on Agent
Hash: 61256976e1939a617f739692c2e112cb33bc922d [PR build]