Introducing PendingIntentController (17/n)

Added PendingIntentController and centralize pending intent handling
in that class. Pending intents are used by activities and other components
like services and broadcasts. Since, activity handling is going to be moving
to the wm package, we need a way to access pending intents from both am and
wm packages. The PendingIntentController allows this to by not holding any
service level locks.

Bug: 80414790
Test: Existing tests pass.
Change-Id: I52f6f233b24e62839a85067556f3560dec27f0c7