[Battery] Add detailed battery controller logs

Add detailed logs for the following events in BatteryControllerImpl:

- Instantiation
- Init
- Every intent action
- BATTERY_CHANGED: level, scale, and whether or not we skip due to test
  mode
- Whenever we send out `onBatteryLevelChanged` callbacks
- Enter/exit test mode

Test: adb shell -n dumpsys activity service com.android.systemui/.SystemUIService BatteryControllerLog
Test: BatteryControllerTest
Bug: 298884211
Change-Id: I395bd638cc66ab60dbd2717233776d8ba25b5368