Persist implicit overlay configurator actor policy

This change does three things:

1) If an overlay targets a package that does not declare an overlayable
   and the overlay fulfills the actor policy, the overlay can override
   any resource in the target,
2) The actor policy is now implicitly granted to overlays signed with
   the same signature as the configurator that target white-listed
   target packages regardless of whether or not the target defines an
   overlayable.
3) If an overlay was previously granted the actor policy through the
   mechanism specified in (2), the overlay will continue to fulfill
   the actor policy even if the configurator is removed, changes
   signature, changes to a different package, or the list of
   configurator targets changes. If the overlay target package or
   target overlayable name changes, the persisted setting will be
   reset.

Bug: 157244814
Bug: 157266239
Test: atest OverlayManagerServiceImplTests
Test: idmap2_tests
Change-Id: Iff3937849ad898b1b2d74c2c632a4cdf7690fe10