These changes make the navigation and status bar accessible from within fullscreen applications by allowing the user to tap on the top or tap or drag on the bottom of the screen.
Also, since the top panel is now over top of all fullscreen applications, this moves the action drawer swipe area back into the status bar.
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.
This allows us in the future to use mobileshell without having the WindowUtil singleton loaded (which does a bunch of wayland calls that aren't necessary for most applications).
