Add onConnectedDeviceChanged() onServiceConnected() callback

- Add onConnectedDeviceChanged() callback to notify MediaDevice
  to change their connect state.

- Add onServiceConnected() to handle profile not ready
  case. The profile may not ready when calling startScan().
  Device status are all disconnected since profiles are not ready to connected.
  In this case, we observe onServiceConnected() in LocalBluetoothProfileManager.
  When A2dpProfile or HearingAidProfile is connected will call buildBluetoothDeviceList()
  again to find the connected devices.

Bug: 121083246
Test: make -j50 RunSettingsLibRoboTests
Change-Id: I6d8bacb9bbd2221eb8c97bbd0419b4e8c9d8dfea