“Bluetooth Audio Codec” is not getting listed while searching for it using...

 “Bluetooth Audio Codec” is not getting listed while searching for it using “keywords” from settings search tab

-Implement PreferenceControllerMixin to decide nonIndexableKeys list according to isAvailable() status

Bug: 156337281
Test: make -j50 RunSettingsRoboTests
Change-Id: I8787acfd50ac351499781d016a3c806a1a6b4f9f