In PowerUsageBase, it will store battery stats if it has a configuration
change, which will make BatteryStatsLoaderHelper never get the correct
battery stats because it uses Bundle.EMPTY as the bundle message.
This cl:
1. Remove the store action even though it is configuration change.
2. Always use null to get battery stats
3. Always start a battery status check in register()
Bug: 63658232
Test: RunSettingsRoboTests
Change-Id: Ifbf970c63378ed66dddcdae4d952b7d1fd84216a
It takes 3-4 seconds to load the battery settings page in Ryu. Main
reason is that it takes too long to init BatteryStatsHelper.
This cl moves loading code to AsyncLoader, and we will refresh ui once
the loading part is finished.
Following cl will add animation for the battery header to make it not
so janky
Bug: 37196170
Test: RunSettingsRoboTest
Change-Id: I40dfdde4a072e28a56c8fdf0ec6d671b5109fc6d
