JobScheduler: Move the concurrency calculation to a separate class

Bug: 111360323

Test: atest CtsJobSchedulerTestCases

Summary
-------
CtsJobSchedulerTestCases: Passed: 28, Failed: 5

5 tests failed
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android.jobscheduler.cts.ConnectivityConstraintTest#testConnectivityConstraintExecutes_metered
android.jobscheduler.cts.ConnectivityConstraintTest#testConnectivityConstraintExecutes_withMobile
android.jobscheduler.cts.ConnectivityConstraintTest#testConnectivityConstraintExecutes_withWifi
android.jobscheduler.cts.ConnectivityConstraintTest#testUnmeteredConstraintExecutes_withWifi
android.jobscheduler.cts.ConnectivityConstraintTest#testUnmeteredConstraintFails_withMobile

 * Connectivity test failures are expected.

Change-Id: I0cf7553dc846b310887da6ae48abd5c19d25b4b4