Adds registering and unregistering of FabricatedOverlay to the OMS.
The process that creates the fabricated overlays owns it and is the
only process allowed to unregister it.
When a fabricated overlay is registered, overlay settings for it are
initialized in all users. When a fabricated overlay is unregistered,
it is disabled and removed from all users. When a new user is created,
it will be able to use the fabricated overlay as well.
On boot, fabricated overlays that are not referenced in overlay
settings will be deleted.
When the package that created the fabricated overlay is uninstalled,
its fabricated overlays are also unregistered.
Bug: 172471315
Test: atest OverlayDeviceTests
Change-Id: I0539656f4c919246b13129579b0286c08a398dc2
6a2ca782d4