Adding multiuser pendingintent linting to default Android linting

Creates a Lint warning for usages of `PendingIntent.getActivity`.

This is a heuristic for identifying calls that may not be multiuser-aware, with the suggested solutions being using `PendingIntent.getActivityAsUser()`.
Bug: 314301774
Change-Id: Id784435c436e172be99c6e5c390cebe1ddcf6697
Test: atest PendingIntentGetActivityDetectorTest -c
Flags: EXEMPT lint check