Bug 1072811 - [Bluetooth] BluetoothHelper APIv2 support

Note:
Following tests of pairing methods will be useless in version 2. We have to use `defaultAdapter.pairingReqs.onpairingconfirmationreq` dom request to respond platform. Not use adapter to configure.
Ref: https://wiki.mozilla.org/B2G/Bluetooth/WebBluetooth-v2/BluetoothAdapter#pairingReqs