Broadcast CEC power status changes

If CEC 2.0 is used, broadcast power status changes to the network.
Transient power status changes are only broadcast when they are expected
to last >2s.

Bug: 166227834
Test: atest com.android.server.hdmi
Change-Id: I888c8d2aa6bcaca65c0db0de0195f1c3939465e9