This commit writes options as immutable to the config file ([$i]
suffix), so that user defined options from desktop do not override our
specified mobile settings.
This commit also moves kdeglobals settings to be written to
~/.config/plasma-mobile/kdeglobals rather than directly to
~/.config/kdeglobals, continuing the work from
!723
Fixes https://invent.kde.org/plasma/plasma-mobile/-/issues/467
