Rework thermal throttling.

1. Stop limiting thermal restriction to only connectivity jobs
2. Throttle all non-EJ background jobs when the status is SEVERE
3. Throttle all bg jobs (including EJ) when the status is CRITICAL

Bug: 193269111
Test: atest frameworks/base/services/tests/mockingservicestests/src/com/android/server/job
Test: atest frameworks/base/services/tests/servicestests/src/com/android/server/job
Test: atest CtsJobSchedulerTestCases
Change-Id: I306a199e2ec6441075c69858000c28f8266eefad