(consider) replace multiple queues with single topic

[myawnhc]

Currently, the preAuth map listener writes the same transaction to multiple queues in order to pass it to different RuleExecutors for processing. This is an expensive duplication - maybe not too bad if executors are keeping up, but will quickly become an issue if executors fall behind.

A pub/sub model using ReliableTopic seems preferable.

The current RuleExecutor is built around CompletableFuture and works well with the IQueue.take mechanism for input; it's not clear how to adapt this to the event-driven onMessage style of a topic.