Partial #2975 - Deprecate v1 Menu classes

[tig]

Fixes

• Partial Modernize Menu - Base on Bar and address litany of issues #2975
  • Fixes HighlightStyle.Hover causes ColorScheme issues #4014
  • Fixes Add events for GetNormalColor etc.... #4016

Proposed Changes/Todos

• Fix UICatalog bugs in v2win/v2net
• Add Fluent menubarv2 tests
• Mark v1 classes as obsolete
• Fix HighlightStyle.Hover causes ColorScheme issues #4014
• Fix Add events for GetNormalColor etc.... #4016

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

[tig]

In the above the Diagnostics menu's FlagSelector menu item has been tweaked to do the right thing.

The other two menus exhibit the old, broken behavior.

[Copilot]

Copilot reviewed 49 out of 49 changed files in this pull request and generated no comments.

Comments suppressed due to low confidence (2)

Terminal.Gui/Views/FlagSelector.cs:437

• The condition in the UncheckNone method unchecks all checkboxes except those labeled 'None', which may be unintended. Consider changing the condition to check for equality ('sv.Title == "None"') to only uncheck the 'None' checkbox.

foreach (CheckBox cb in SubViews.OfType<CheckBox> ().Where (sv => sv.Title != "None"))

Terminal.Gui/Views/Menu/PopoverMenu.cs:408

• [nitpick] If the commented-out border styling code is no longer needed, consider removing it for clarity. Otherwise, add an explanatory comment describing its retention.

//menu.Border.Thickness = new (1);

[tig]

New MenuBarv2.EnableForDesign menu and Menus Scenario

[tznind]

I have also fixed 92aae38 in #4029 (in 58b0178) with various followups in TableView ect and delete dead code.

Only mentioning to try and avoid duplicated effort/merge conflicts