Move JobServiceContext handling to the concurrency manager.

Move handling of the set of JobServiceContexts to the concurrency
manager to make it easier to make the list dynamic and flexible in the
future.

Bug: 141645789
Bug: 223437753
Test: atest CtsJobSchedulerTestCases
Test: atest frameworks/base/services/tests/mockingservicestests/src/com/android/server/job
Test: atest frameworks/base/services/tests/servicestests/src/com/android/server/job
Change-Id: I9cf61131700321509800aef0867c911178f80383