Keep Bluetooth module hot to quickly swith it on/off

Add BluetoothAdapterStateMachine to maintain a inter state machine other than
the public BluetoothAdapter states. This is a improvement to BluetoothService
code. 2 internal state are added, LoadingFirmware and FirmwareLoaded to place
the Bluetooth module in a ready-to-switch-on state so that it can be quickly
switched on to have a better user experience
bug 5021787

Change-Id: Ia352e88cba509d9e98c900f85e7479f8cee1de5e