Add a global setting to turn on/off the proc state cpu times tracking.

Bug: 66953194
Test: atest core/tests/coretests/src/com/android/internal/os/BatteryStatsTests.java
Test: atest hostsidetests/incident/src/com/android/server/cts/BatteryStatsValidationTest.java
Test: atest core/tests/coretests/src/com/android/internal/os/BstatsCpuTimesValidationTest.java
Change-Id: Id26476ad77c95994f358d8bd59b6c2e6513c4c54