Refactors TabView using modern v2 capabilties

[tig]

TabView is a great control for testing the library. It has a lot of capabilities that stretch the library. The v1 version was internally very complex in order to work around limitations in TG. In theory, v2 should enable making this control a lot simpler.

This PR is a WIP/Prototype that I started to determine if we're on the right track with these v2 capabilities:

• Content scrolling - The TabRowView can/should just be a horizontally scrolling View where each Tab is just a subview. All the complex TabView logic for renering the Tabs and supporting scrolling can go away.
• Layout - Dim.Auto, deferred layout, etc... should reduce the need for a lot of the internal complexity. Especially the complex layout math scattered around.
• Drawing - There should be no need for TabView to draw lines directly. Each element can just be a View and leverage Border an automatic line joins currently enabled by SuperViewRendersLineCanvas
• Navigation - How a user navs with the keyboard across Tabs, TabRowView, and the tab content is complex. The new v2 Nav system should make this easier.

Depends on

• Fixes #3761, #2886, #3780, #3485, #3622, #3413, #2995 - Draw and Layout performance/correctness #3798

In #3798 auto-line join across Views is currently broken. I'm pausing work on this PR until I fix that.

Fixes

Proposed Changes/Todos

• Prototype TabRowView that just uses content scrolling
• Remove ContentView
• Remove all complex LineCanvas stuff and just rely on Border

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

[BDisp]

There is still a little flickering and the selected tab isn't draw with the focus attribute.

[tig]

@BDisp - I somehow screwed this PR up and while it merged with v2_develop, it's not actually there.

Not sure what I did. Trying to fix it now.

[BDisp]

@BDisp - I somehow screwed this PR up and while it merged with v2_develop, it's not actually there.

Not sure what I did. Trying to fix it now.

Don't forget that my PR #3828 already fix this.