Add throttling by job run session.

A session is considered a period of time when jobs for an app ran.
Overlapping jobs are counted as part of the same session. This adds a
way to limit the number of job sessions an app can run. This includes a
mechanism to coalesce sessions -- if a second session started soon after
one just ended, they will only be counted as one session.

Bug: 132227621
Test: atest com.android.server.job.controllers.QuotaControllerTest
Test: atest CtsJobSchedulerTestCases
Change-Id: Id2ac4037731f57547d00985e8d549b9e990a5f3e