Automatically turning off battery saver at a high percentage.

This introduces a setting that turns off sticky Battery Saver above a
certain threshold and disables Battery Saver if it was enabled due to
the sticky setting.

Bug: 112232746
Test: atest com.android.server.power.batterysaver.BatterySaverStateMachineTest
Test: atest android.provider.SettingsBackupTest
Change-Id: Ib9a9fd627a56529404b41fbabedf8bb4a372074e