BatteryController: Notify listeners from DeviceMonitor

Notify listeners directly from DeviceMonitor on poll, UEvent, or on
configuration changes whenever the reported state changes. Do not report
any changes if only the timestamp changes.

There should be no behavior changes in this CL.

Bug: 243005009
Test: atest FrameworkServicesTests
Change-Id: Ie234319ccf1b89532e7392e221bce5f5dd740fbe