Include WinForms trimming feature switch information

[LakshanF]

The feature switches related to WinForms trimming that are not yet defined in runtime trimming should be updated on a relevant WinForms target file or at Microsoft.NET.ILLink.targets and documented.

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[MichalStrehovsky]

These would ideally be in WinForms-specific .targets. The feature switches we keep in the ILLink targets are specific to dotnet/runtime repo. We don't e.g. define feature switches for ASP.NET in this file. (Might want to move the issue to WinForms.)

[LakshanF]

This work is done via dotnet/winforms#11568 for the default values when trimming, and dotnet/sdk#41702 for the RuntimeHostConfiguration propagation.

Documenting is via #104673