* Add BluetoothDevice.getBatteryLevel() API to retreive battery level
information of remote device
* Add BluetoothDevice.ACTION_BATTERY_LEVEL_CHANGED intent to notify user
that remote device's battery level has changed
Bug: 35874078
Test: make, pair with devices and use them
Change-Id: I41051ee25383f5f3a1e505aef6f8c526385f58bd
Merged-In: I41051ee25383f5f3a1e505aef6f8c526385f58bd
(cherry picked from commit 1d312bfa78)