[dotnet-watch] Parallelize more tests

[tmat]

Parallelizes more dotnet watch tests and adds a Copilot-generated script that helps analyzing test output.

eng\scripts>dotnet run analyze-watch-test-output.cs https://helixr1107v0xdeko0k025g8.blob.core.windows.net/dotnet-sdk-refs-pull-53192-merge-774a9bfb9c424be389/dotnet-watch.Tests.dll.1/1/console.cbc81d8a.log?helixlogtype=result
Downloading https://helixr1107v0xdeko0k025g8.blob.core.windows.net/dotnet-sdk-refs-pull-53192-merge-774a9bfb9c424be389/dotnet-watch.Tests.dll.1/1/console.cbc81d8a.log?helixlogtype=result...
Downloaded to Temp\console.cbc81d8a.log
Wrote Temp\console.cbc81d8a.html (64 tests, 5347 input lines)