Remove the old battery page

This CL removes PowerUsageSummaryLegacy and PowerUsageAdvancedLegacy
and their related layouts and strigns.

Also remove the isBatteryV2Enabled method in feature provider.

Change-Id: I1ec30f713d733ed24335a3e698fb515751232948
Fixes: 76027338
Test: robo test still pass
18 files changed