🚧 .NET Standard extraction from the Toolkit

[XAML-Knight]

The .NET Standard Code has been moved to a new repo, and is no longer meant to be maintained by the Windows Community Toolkit repo.

Fixes #4382

PR Type

What kind of change does this PR introduce?

• Refactoring (no functional changes, no api changes)

What is the current behavior?

The Community Toolkit contains .NET Standard code

What is the new behavior?

.NET Standard code is removed from the toolkit. Specifically, it's these projects and associated unit tests that are being removed:

• Microsoft.Toolkit
• Microsoft.Toolkit.Diagnostics
• Microsoft.Toolkit.HighPerformance
• Microsoft.Toolkit.Mvvm
• Microsoft.Toolkit.Mvvm.SourceGenerators

Code that previously depended on the Microsoft.Toolkit code was updated to instead grab from the CommunityToolkit.Common NuGet package (MainLatest).

PR Checklist

Please check if your PR fulfills the following requirements:

• Tested code with current supported SDKs
• New component
  • Pull Request has been submitted to the documentation repository instructions. Link:
  • Added description of major feature to project description for NuGet package (4000 total character limit, so don't push entire description over that)
  • If control, added to Visual Studio Design project
• Sample in sample app has been added / updated (for bug fixes / features)
  • Icon has been created (if new sample) following the Thumbnail Style Guide and templates
• New major technical changes in the toolkit have or will be added to the Wiki e.g. build changes, source generators, testing infrastructure, sample creation changes, etc...
• Tests for the changes have been added (for bug fixes / features) (if applicable)
  • Tests which were duplicating those appearing in the dotnet repo have been removed
• Header has been added to all new source files (run build/UpdateHeaders.bat)
• Contains NO breaking changes

Other information

[ghost]

Thanks XAML-Knight for opening a Pull Request! The reviewers will test the PR and highlight if there is any conflict or changes required. If the PR is approved we will proceed to merge the pull request 🙌

[XAML-Knight]

Moved effort over to new PR #4395