Disable the optimization mode preference if the app is not settable

https://screenshot.googleplex.com/BbQyEv6YCjPVwUF (allowlist)
https://screenshot.googleplex.com/3hTb8TQwGMQqcwS
https://screenshot.googleplex.com/6hdTAT2yNFucD9N (system app)
https://screenshot.googleplex.com/77T5JyAD5nZJpDT (normal app)

Fix: 281566984
Test: make test RunSettingsRoboTests ROBOTEST_FILTER=com.android.settings.fuelgauge.*
Change-Id: If7aa4b61bc806daa570187da24b7f454cd069dec