Continuing Implementation of #3692 - Second round of ConsoleDriver cleanup

[dodexahedron]

Continuing from the end of the branch in #3710, for #3692.

This one started off with me going after MainLoop, but quickly turned into working on the rest of the Windows driver implementations, in the WindowsDriver and WindowsConsole classes.

So, that's where it will continue to focus and what this one will be mostly contained to.

Note that the commit list and diffs show everything back to the start of #3710, but will reduce to starting at the end of #3710, once that is merged.

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Proposed Changes/Todos

• More one-type-per-file splits.
• Refactoring WindowsDriver/WindowsConsole to use the new PInvoke style and avoid PInvokes via direct use of the FileStreams on the console handles, as with Implements #3692 - First round of ConsoleDriver cleanup #3710.
• Ideally consolidating WindowsDriver and WindowsConsole into one class, if prudent.
• Standardize the API of WindowsDriver and NetWinVTConsole, working toward unifying all drivers under the same abstraction.
• Whatever else comes along

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

I pushed the branch in its state before I did more work, yesterday, when I was rebasing the other branch anyway. Not a whole lot to see, yet, though a couple of PInvokes have been jostled around a bit. Not to be considered stable at current head of this branch, at the moment. Was just a sync.

WIP

[dodexahedron]

Closing this one, as well, for same reason mentioned in #3710

Will open new PRs when I have drafts or merge-ready stuff ready after some more drawing board time.