[Pair hearing devices] Extract common behavior in BluetoothPairingDetail into Base class

* Before adding new hearing device feature, we will extract the common part into Base class first. They will share most of the UI component.

Bug: 237625815
Test: make RunSettingsRoboTests ROBOTEST_FILTER=BluetoothDevicePairingDetailBaseTest
Test: make RunSettingsRoboTests ROBOTEST_FILTER=BluetoothDevicePairingDetailTest
Change-Id: I3a44c4c464d630fdcafa151afc82d3000fd728a3
5 files changed