Refactor/unify rate-limiting code in NotificationManager

Also rate-limit the logcat logging of said rate-limiting (heh). This logic will be shared with the upcoming logging to statsd (via either atoms or counters, TBD).

Observable behavior is the same, so NotificationManagerTest has no changes.

Bug: 381875150
Bug: 384467103
Test: atest NotificationManagerTest
Flag: android.app.nm_binder_perf_throttle_notify
Change-Id: I16d264e13ce795306560b716153aae7819f07b66