Acquire WakeLocks for posting notifications

The WakeLock is acquired by the system (with Binder.clearCallingIdentity()) because packages that post notification may not have (and should not need) the WAKE_LOCK permission, but we use the WorkSource so that the battery impact is counted as coming from them.

Bug: 275044361
Flag: WAKE_LOCK_FOR_POSTING_NOTIFICATION
Test: atest NotificationManagerServiceTest
Change-Id: Ide41df01dec38631bbdacbd268415d471fed6a3d