Enhance APP_BACKGROUND_RESTRICTIONS_INFO log.

Only log APP_BACKGROUND_RESTRICTIONS_INFO when the restricion level
change causes update to AppStandbyController.

Besides the new restriction level, also log previous restriction level,
so we know restriction level changed from where to where.

Fill in BatteryTrackerInfo if tracker type is BatteryTracker. Add fields
foreground and cached battery usage in BatteryTrackerInfo.

Bug: NA
Test: statsd_testdrive 441
Change-Id: Ie9cf8b8d17c37fad7ee2a26ba3c0e323a6f1e374