Add a settings page to halcyon, which allows for toggling whether the
wallpaper is blurred and double tapping on the homescreen to lock the
device. This also does a bit of refactoring for folio and halcyon to
share the same wallpaper blurring item.
Contributes to #317
This refactor changes WindowMaximizedTracker from being a Singleton, and allows for it to be created in a way such that screens can be filtered out.
This fixes external screens from having their homescreen "zoom out" when an app is maximized on another screen.
The eventual goal is to have as few singletons with state as possible in the mobileshell component when it is imported into components such as the lockscreen.
This doesn't fully accomplish it, but moves the audio provider singleton to MobileShellState, which will eventually need to be prevented from importing into non plasmashell processes.
This also disables the sound feedback when changing volume, since it can be a source of lag when showing the applet.
Having a global set margins and orientation (that were calculated from the panel containment) caused a lot of issues with the way bindings were evaluated across panels, and with high coupling.
Now use properties from within containments to determine shell margins instead, which removes the dependency on other containments for measurements. This allows us to get rid of TaskPanelControls as well!
Fixes: https://invent.kde.org/teams/plasma-mobile/issues/-/issues/198
