Add anomaly icon for PowerGaugePreference

When the app contains anomaly, we should show anomaly icon(triangle
alert).

This cl also extracts a new method refreshAppListGroup from refreshUi.
New method is used to only refresh appListGroup. Reason for this action:

1. Improve performance(partial refresh)
2. We init AnomalyLoader in refreshUi, invoke refreshUi in
onLoadFinish will create infinite loop.

Bug: 36924669
Test: RunSettingsRoboTests
Change-Id: If54c89349e21763ca714123ac6ae884bd0f6a377