Clean Up Sending Agents that Appear to be Idle #1908

If a SendingAgent has not been used in X amount of time, have Wolverine shut it down and reclaim it. This is mostly around control queues and reply queues that may be obsolete.

It's really only a big concern for Rabbit MQ senders to ephemeral queues. Reply & control queues. Might matter for other places too.

The problem is that we really need to know which sending agents are potentially ephemeral, and which ones are durable.

Put this aside for the moment. Come back and do it by tracking which sending agents are part of control or reply endpoints.