batch queue: add queue initialization to server

[mismithhisler]

Description

These changes add the create and start of a batch queue interface implementation to the Nomad server, along with changes to how we route job registration evaluations, so batch job evaluations are routed to the batch job queue.

Testing & Reproduction steps

Links

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Changes to Security Controls

Are there any changes to security controls (access controls, encryption, logging) in this pull request? If so, explain.

[allisonlarson]

This makes sense to me! Keeping the queue routing in the FSM feels like the right move, to echo @tgross in the earlier review, even if it is a bit wonky right now.

[mismithhisler]

@tgross @allisonlarson Agreed that doing this in the FSM ended up being the best route. Also, injecting the state via SetEnabled similarly to the DeploymentsWatcher made this a little less weird.