Remove references to BatterStatsHelper from BatteryUsageStatsProvider

Also, add BatteryUsageStatsQuery.getMaxStatsAge() to allow throttling
of battery stats sync.

Bug: 174186345
Test: atest FrameworksCoreTests:com.android.internal.os.BatteryStatsTests
Change-Id: I097c6b9575422837a522cf313a320e83221cdfab
6 files changed