Move RPM stats collection out of BatteryStatsImpl.mLock

Querying RPM stats on device with a large number of StateResidency info
can take a long time. Move the query to outside of the BatteryStats
lock to reduce the chance of lock contention.

Bug: 185970842
Test: atest android.cts.statsd.validation.ValidationTests#testPartialWakelock

Change-Id: I1c69b3f9c071e5d758cf4b22855c4b0ec221a5cf