Project-system: Port WinFormEditorProvider from CPS to here

[davkean]

This adds support for opening a WinForms designer from a source file:

https://devdiv.visualstudio.com/DevDiv/_git/CPS/pullrequest/134764?path=%2Fsrc%2FMicrosoft.VisualStudio.ProjectSystem.VS.Implementation%2FEditor%2FWinFormEditorProvider.cs&discussionId=1355860&_a=files

[davkean]

Should put this behind a new capability describing WinForms.

[filipnavara]

Any way to make the code available to non-Microsofties?

[wjk]

@davkean Since the milestone is 16.2, does this mean that the changes required to support the WinForms designer in a Core project will ship in the VS 16.2 update? If so, I can't wait.

Also: Are there any issues (related to WinForms designer support or otherwise) I could help out and create a PR for? Thanks!

[davkean]

WinForms for .NET Framework scenarios should quasi work (sans a few bugs) in 16.1. 16.2 we fixed a few more bugs, but there's nothing more to really do. This bug is just a cleanup bug for layering purposes.

WinForms for .NET Core is very far away and cannot give you a timeframe, the majority of work for this is in closed source so nothing really to help. Our help wanted issues are tracked via https://github.com/dotnet/project-system/issues?q=is%3Aopen+is%3Aissue+label%3A%22Help+Wanted%22.

[davkean]

This is merged in, I'll leave it open to track the deletion of the CPS code.

[davkean]

This is now done.