Limit the number of persistable JobWorkItems.

Add a limit to the number of JobWorkItems that can be enqueued when the
job and work items are to be persisted.

Bug: 255352252
Bug: 273758274
Test: atest FrameworksMockingServicesTests:JobSchedulerServiceTest
Change-Id: Icca042f7d8d11b6d74e222fcde10521d3f130821