Use different source metric categories to distinguish different launch sources of the BluetoothPairingDetail page.
Bug: 237344016
Test: manual
Change-Id: If762e87414055f3e497f99ea6885f7736b7193cd
* 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