[kcmkwin/kwinoptions] Add GUI for making KDE apps not remember window positions
This adds a setting to the window options KCM to prevent 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.
This setting is hidden on Wayland, as it is 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 frameworks/kxmlgui!14 (merged) for more details regarding the reasons why this might be desirable.
Test plan:
- Apply frameworks/kxmlgui!14 (merged) to kconfig
- Apply this to kwin
- Launch Dolphin, move its window, close it, and re-launch it -> See that window position was remembered
- Launch Window Options KCM > Advanced Tab > Uncheck "Allow KDE apps to remember the positions of their own windows" > Click Apply
- Launch Dolphin again -> See that it was positioned according to the KWin placement mode rather than remembering its prior position
CCBUG: 415150