system_server: create StatsManagerService

Refactor to split the logic within statscompanion_service
The goal of the refactor is to simplify the binder calls to statsd

This service will talk to statsd.

At the end of the refactor, this service should be the only
service that talks to statsd.

Bug: 146074223
Test: Manual by creating the service with empty implementation
Change-Id: Ib9c2e10ec195d41062f1001e5a82b374696de939
4 files changed