This adds a setting to the window options KCM to disable KDE apps
remembering their own window positions on X11, and instead always use
the KWin placement modes.
The setting sets an option in `kdeglobals`, rather than kwinrc, as it is not
a KWin-specific option *per se*. The UI is also hidden on Wayland, as it it
not relevant there because the functionality it disables does not work on
Wayland. Instead, remembering window positions will eventually be implemented
in a different way and affect all windows, not just KDE windows.
See https://invent.kde.org/frameworks/kxmlgui/-/merge_requests/14 for
more details.
CCBUG: 415150
