[IT01] Move power state stats logging out from NMS

In order to support ConnectivityService mainline, the dependency
with NMS should be removed. The idle timer control API should be
replaced with calling INetd interface instead of using NMS hidden
API. However, NMS has more logic than setting the idle timer to
netd. If CS would like to send idle timer setting to netd directly
, those logic should be handled by CS itself or moved to other
equivalent places.

The power state is sent to BatterystatsService and logged the
corresponding metrics at the same time, so writing metrics should
be able to put together inside BatteryStatsService.

Bug: 170598012
Test: m and use statsd_testdrive to verify
Change-Id: Iadfa3671ed34bf403be8b53eb47f83386b22c85a