Split DomainModelControllerService into separate services for initializing as a master versus as a slave

This is an aspect of WFCORE-338, although it's valid in its own right as a conceptually cleaner approach to host controller boot.

Using different services is a prerequisite to WFCORE-338 as it allows those elements of HC behavior to be started/stopped as a DC candidate is elected or unelected. It also makes it feasible to wire in the service that performs the election.

The method that installs the service with MSC will return a Future<Boolean>, with the service setting the future's value at the completion of start(). DMCS during boot can block reading the future, from that confirm that the service completed successfully, and then proceed with the rest of boot. The boolean is basically an ok/not ok signal.