[dotnet test][MTP]: Failing to run solution filter that contains shproj

[Youssef1313]

During Uno Platform migration to MSTest v4, MTP v2, and the MTP-based dotnet test, the following error was found:

Unhandled exception: One or more errors occurred. (The imported file "$(MSBuildExtensionsPath32)\Microsoft\VisualStudio\v$(VisualStudioVersion)\CodeSharing\Microsoft.CodeSharing.Common.Default.props" does not exist and appears to be part of a Visual Studio component. This file may require MSBuild.exe in order to be imported successfully, and so may fail to build in the dotnet CLI. C:\a\1\s\src\SourceGenerators\SourceGeneratorHelpers\SourceGeneratorHelpers.shproj)

PR: unoplatform/uno#21645

Shared project: https://github.com/unoplatform/uno/blob/775a1ba37614d6c9e8a359a8e69097db00384915/src/SourceGenerators/SourceGeneratorHelpers/SourceGeneratorHelpers.shproj

The case here is a shared project in solution filter, which doesn't seem to work and fails with the above error.

This is currently a blocker for Uno Platform to be able to adopt MSTest v4.

@rainersigwald @baronfel Any suggestions here?

[Youssef1313]

We are misusing the API for parsing solution files. We just take all projects blindly, but not everything is "buildable".

shproj is one example, but there are more.