Fixes #2799. Adds TrueColor support to NetDriver

[tig]

• Fixes Add TrueColor support to NetDriver #2799
• Supports Windows Terminal
• Supports conhost
• Supports WSL
• Improves WindowsDriver too (ensures Force16Color is true when not running in WT).
• Adds diagnostics flag to UICatalog (need to add ConfigurationManager setting too.
• Updates unit tests to test new flags (and makes progress on letting all consoledrivers work in unit tests)

Pull Request checklist:

• I've named my PR in the form of "Fixes #issue. Terse description."
• My code follows the style guidelines of Terminal.Gui - if you use Visual Studio, hit CTRL-K-D to automatically reformat your files before committing.
• My code follows the Terminal.Gui library design guidelines
• I ran dotnet test before commit
• I have made corresponding changes to the API documentation (using /// style comments)
• My changes generate no new warnings
• I have checked my code and corrected any poor grammar or misspellings
• I conducted basic QA to assure all features are working