Pop up pairing another ear dialog when detecting hearing aid is a set

* Pop up dialog in 'Connected deivce' page and 'Accessibility -> Hearing
  aids' page

Bug: 225117454
Bug: 226511985
Test: make RunSettingsRoboTests ROBOTEST_FILTER=HearingAidPairingDialogFragmentTest
Test: make RunSettingsRoboTests ROBOTEST_FILTER=AvailableMediaDeviceGroupControllerTest
Test: make RunSettingsRoboTests ROBOTEST_FILTER=AccessibilityHearingAidPreferenceControllerTest
Test: make RunSettingsRoboTests ROBOTEST_FILTER=HearingAidUtils

Change-Id: I34a1e3ac680a7efe97dc501bfbe93f840ad16364