[BuildCheck] Editor config support

[f-alizada]

First iteration of the code with latest merged changes from exp/build-analyzers.

Design capturing current implementation could be viewed here: https://github.com/dotnet/msbuild/tree/dev/f-alizada/support-editorconfig/src/Build/BuildCheck/Infrastructure/EditorConfig

Discussions:

• Discuss the prefix for the rule in editorconfigfile - for now it will be left as it is and discussed solved in scope of this ticket: Research and implement rules/analyzers identification and filtering strategy #9823

Current implementation.
The editorConfig parsing functionality is being used by https://github.com/dotnet/msbuild/blob/dev/f-alizada/support-editorconfig/src/Build/BuildCheck/Infrastructure/ConfigurationProvider.cs
to fetch all configs from .editorconfig.

• Add comments on all public APIs
• Check the case sensitive key-values in cache
• Manual testing
  • unix
  • windows

[JanKrivanek]

First quick pass. Looks good! :-)
Though I'd love to see my static leftover being turned into mockable interface

I haven't reviewed the copied files though... (hopefully we'll anyways end up consuming a shared version from Roslyn)

[JanKrivanek]

I added couple additional comments

[rainersigwald]

Design capturing current implementation could be viewed here: https://github.com/dotnet/msbuild/tree/dev/f-alizada/support-editorconfig/src/Build/BuildCop/Infrastructure/EditorConfig

Can you add to this doc some details about what the exposed interface to this stuff is? That is, what interfaces/whatever MSBuild code will be using to learn about editorconfig-driven configuration?

Also, does this PR introduce the patterns that we'll use to map (stuff in the .editorconfig) to (severity for rules), or is that coming later?

[JanKrivanek]

Re-reviewed latest state - looks goot to go for initial version!

[f-alizada]

Can you add to this doc some details about what the exposed interface to this stuff is? That is, what interfaces/whatever MSBuild code will be using to learn about editorconfig-driven configuration?

Added example of the usage (API) and what it returns.

Also, does this PR introduce the patterns that we'll use to map (stuff in the .editorconfig) to (severity for rules), or is that coming later?

The PR introduced both -> .editorconfig parsing and mapping the configuration to the actual rules

[JanKrivanek]

I haver couple comments for consideration - but overall looks good!

[JanKrivanek]

Thnak you for all the improvement roundtrips on the PR!

[ladipro]

Thank you!