* Extract the common part into HearingAidHelper.
* Remove abstract getHearingDevice(). Change to get the hearing device when needed.
* Move several classes from Bluetooth into Accessibility
Bug: 281783079
Test: make RunSettingsRoboTests ROBOTEST_FILTER="(HearingDeviceAudioRoutingBasePreferenceControllerTest|AccessibilityHearingAidPreferenceControllerTest|HearingAidHelperTest|HearingAidAudioRoutingPreferenceControllerTest|HearingDeviceCallRoutingPreferenceControllerTest)"
Change-Id: I79049107409b7086c6dcc8d48a6323e171ed1535