Add CountQuotaTracker.

This adds a utility class that can track instantaneous app behavior and
manages count quotas for the owning system. A system service just needs to
create a tracker, set the limits, and call the relevant APIs to determine
what to do for each behavior. JobScheduler will use it to prevent apps from
calling JobScheduler.schedule() too often.

Bug: 135764360
Test: atest CountQuotaTrackerTest
Change-Id: Iacd4286bd7f4ab3fc428d8e2ec573671b287f225