1. Make BatterySaverSettings extend from DashboardFragment
2. Add new layout
3. Add battery saver controller
Future cl will add controllers for seekbar and button
Bug: 72228477
Test: RunSettingsRoboTests
Change-Id: I21fb62aef874c04eca2988271f2fd9d7aacb0c6c
Create PowerUsageSummaryLegacy and power_usage_summary_legacy, which
contains the old implementaion.
Bug: 69797586
Test: RunSettingsRoboTests
Change-Id: Icb9c25f06889462a6eedea48ae166043a6636848