Add allowlist mechanism for battery optimization mode

Add a mechanism to add package name into the allowlist to avoid users
change the battery optimization modes for specific apps in the list

https://screenshot.googleplex.com/8hrHCcTh5bNYXqp

Bug: 281566984
Test: make test RunSettingsRoboTests ROBOTEST_FILTER=com.android.settings.fuelgauge.*
Change-Id: I8efa6a55646d761f5bee3667a59b38ab68c74bc1