Move AppHibernationServices dependencies to injector

Similar to other system services, we move AppHibernationService's
dependencies to an injector class that can be mocked for testing so that
we minimize side-effects in unit tests

Also, add @GuardedBy annotations instead of having an L at the end of
method names since this is exactly what the annotation is for.

Bug: 175829330
Test: atest AppHibernationServiceTest
Change-Id: Iec51a349ff898923bacf6040c3ebccefa8831a68