Allow system jobs to be exempted from app-standby
This flag will allow the sync manager to exempt certain kind of sync requests.
- This will only exempt jobs from app-standby.
- EBS still won't exempt them. Battery saver cuts background network anyway, so
background syncs will still not work, and it didn't used to work pre-P either.
- Manual force-app standby still doesn't allow them to run.
Bug:
72443754
Test: Build and boot. The behavior shouldn't change since none uses the flag yet.
Test: atest CtsJobSchedulerTestCases
Change-Id: I806b97bb4b7da773479e878e6eccb792b03eadc1