power: Re-introduce custom charging sounds

 * Mostly inspired by old implementation (see commit 72fe3994),
   but refactored to use most of the AOSP code.

 * Also adapted to the wireless charging feature introduced in P
   (note that it was assumed that we should not play any vibration
   when the device is undocked from the wireless charger).

Change-Id: I5f6589002db51fe03ec2cf7bb33ed0e63948c55a