Add a new BatteryStatsManager class

Wifi/telephony mainline modules uses IBatteryStats which is an AIDL &
hence cannot be made a @SystemApi. Create a new manager class to wrap
around this AIDL to expose @System Api.

Bug: 138806762
Test: Device boots up & connects to wifi networks.
Change-Id: Ib8816c3df17ccc562b9664e7bea1ef01ab61f697
7 files changed