Move statscompanion to statsd-service jar

This moves statscompanion to statsd-service.jar, and out of
services.jar, in preparation to add it to the statsd apex. In later CL's
I will start making the communication to the rest of system server go
accross approved boundaries. I will also make a second service in system
server to put pullers and other things that we do not care about
updating.

Test: builds, boots, statscompanion talks to statsd
Change-Id: Id7c36bfe4c2138edd4a19f3f477ce31c2f1973d3