Ttk-based theming

[ElSaico]

Description

This replaces Tk widgets with their Ttk equivalents and makes theme.apply() use actual Ttk themes, which are implemented as Tcl packages.
It also sets the colors for all non-Ttk widgets the correct way, via tk_setPalette, and eliminates the need for most of myNotebook (with the exception of EntryMenu, which has added functionality).

Plugins should be minimally affected, and can be encouraged to use Ttk from then on.

Type of Change

UI. As in, all of it.

How Tested

The application is being live tested with my plugin setup - those with interfaces (main screen and/or preferences) are:

• Artemis Scanner Tracker
• BioScan
• EDMC-C14-SoundViewer
• EDMC-Cannon
• EDMC-Massacres
• Hutton Helper
• SpanshRouter

In addition, a comprehensive catalog of Ttk widgets was added as a core plugin (accessible only with the --ttk-catalog argument), to showcase them for plugin authors and help any future theme development.

Notes

Closes #2116

[ElSaico]

Problem: while yeeting the alternative title bar for the Windows native dark one would rid us of the former's gnarly minimize/restore handling, the Transparent theme doesn't work on the latter - as its background color needs to be the exact same as the rest of the window (and worse, it changes upon deselecting).

The only pre-Windows 11 way to change a title bar's color (at least without invoking a mountain of undocumented Win32 calls that'd defeat its purpose anyway) is through the Windows App SDK, a set of WinRT APIs that work all the way back to version 1809.
There are bindings thanks to PyWinRT, but it lacks a crucial piece: a Win32 interop API that converts HWNDs from existing windows to the SDK's native WindowId. I made a request (pywinrt/pywinrt#61) and the head maintainer is so prolific that it might not take much long to get it implemented, so there's still hope.

...also, this SDK might open the door for cleaner alternatives of our Win32 API sprawl in the future - even beyond the ongoing move to pywin32.