New API methods to access external battery info

Created new API methods that allow apps to access external battery info
of devices such as bluetooth connected gamepads.

Bug: 161633432
Test: atest android.hardware.input.cts.tests.SonyDualshock4BluetoothTest
      atest android.hardware.input.cts.tests.SonyDualshock3UsbTest

Change-Id: Iba59fc9a259818b03c24ee8c2c49601952ed65a3
Merged-In: Iba59fc9a259818b03c24ee8c2c49601952ed65a3