Check opportunistic quota on metered networks.

Check that a job's total estimated data transfer will fit in the
opportunistic quota before allowing it to run on the unmetered network.

Bug: 189104483
Test: atest FrameworksMockingServicesTests:ConnectivityControllerTest
Test: atest CtsJobSchedulerTestCases:ConnectivityConstraintTest
Change-Id: I6d7e83d87dc3d1522c934e7441f4975418d571e7