Exempt carrier privileged apps from flex policy.

Carrier privileged apps can do work that's important for proper
connection and functionality. Therefore, exempt their DEFAULT+ jobs from
flex policy so they're not unintentionally delayed significantly.

Bug: 236261941
Test: atest CtsJobSchedulerTestCases:FlexibilityConstraintTest
Test: atest FrameworksMockingServicesTests:FlexibilityControllerTest
Change-Id: Ic1dfb2b1694f5f33b2200c4af5d3d4c3dfb9e66e