The core thing is to find out a way to update group when devices
(bt device and usb device)are updated.
The infrastructure contains three parts:
1. ConnectedDeviceController
Normal PreferenceController. Get info from sub controller and update
the preferenceGroup.
2. BluetoothDeviceUpdater
Listen to bluetooth callback, decide whether to add/remove devices
3. DevicePreferenceCallback
Interface to add/remove preference. This interface will be used in
ConntectedDeviceController and future SavedDeviceController
Bug: 69333961
Test: RunsettingsRoboTests
Change-Id: I85a9ef216a801d5f0dd1cf0130d53850a68be4bd
