[IT02] Expose system api to report radio power state

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.

The state reporting will be triggered from updating idle timer
and netd unsolicited interface activity changed events.
BatteryStatsService should be able to get the netd event by
registering the listener directly. This commit exposes two system
APIs to report the radio power state for wifi and mobile for
supporting update idle timer from CS directly to INetd.

Bug: 170598012
Test: make update-api ; m
Change-Id: I286d6aa237ecb2653e1464e26a3581b8eeeb9e63