rabbitmq_cluster: limit queue size to 1GB and remove stale queues
    
    When a user creates a queue and then never consumes from it (such at the
    current Greenwave queue) it grows and grows forever. This isn't a
    problem in the short term as messages are very small and 100K messages
    is in the range of 10MB (depending on the payload size, obviously), but
    eventually it will lead to trouble.
    
    This policy will delete any queue that has had no subscribers in 31
    days, and as a safety measure also limits all queues to 1GB of storage,
    which is probably excessive.
    
    Signed-off-by: Jeremy Cline <jeremy@jcline.org>