Add listeners to appops checking interface

Note about locking: AppOpsService calls into the checking service
holding the lock when changing mode then the checking service also grabs
the same lock. It then dispatches the callback synchronously back to
AppOpsService where (in packageModeChanged) that callback grabs the lock
again. This is taking advantage of the reentrant property of java locks
and protects against mutations that may happen outside of this flow.

Test: atest CtsAppOpsTestCases AppOpsServiceTest
Bug: 268696066

Change-Id: I41d79fdba0dcdc56a287082e22663fbc85998fb2