[3.13] gh-128846: Make tkinter tests robust against Tcl/Tk 9.0 (GH-153484)

[3.13] gh-128846: Make tkinter tests robust against Tcl/Tk 9.0 (GH-153484)

Backport the test-only parts of the Tcl/Tk 8.7/9.0/9.1 test adaptations so
that test_tkinter and test_ttk pass when Python 3.13 is built against
Tcl/Tk 9.0 (for example the Homebrew build used on macOS), while still
passing against the Tcl/Tk 8.6 that 3.13 ships.

Combines the test changes from:

* gh-124111: Update tkinter for compatibility with Tcl/Tk 9.0.0 (GH-124156)
* gh-124111: test macOS CI with Tk 9 (GH-137424)
* gh-145736: Fix Tkinter tests for Tk 8.7, 9.0 and 9.1 (GH-145738)

The corresponding non-test changes (Modules/_tkinter.c, Lib/tkinter/ttk.py,
PCbuild and CI configuration) are not backported.