Add tkinter wrappers for the wm stackorder, wm iconbadge and winfo isdark commands

[serhiy-storchaka]

A few Tk window-management commands have no tkinter wrapper and are currently reachable only through tk.call().

• wm stackorder (since Tk 8.4) returns the toplevel windows in stacking order, and can also report whether one toplevel is above or below another.
• wm iconbadge (new in Tk 9.0) sets a badge (a number or an exclamation point) on the application icon in the Dock, taskbar or app panel.
• winfo isdark (new in Tk 9.0) reports whether a window is in "dark mode" on macOS and Windows.

I propose to add the corresponding Wm.wm_stackorder(), Wm.wm_iconbadge() and Misc.winfo_isdark() methods (with the usual stackorder and iconbadge short aliases for the wm methods).

Linked PRs

• gh-151874: Add tkinter wm_stackorder, wm_iconbadge and winfo_isdark #151875