Add hashing algorithm to load balance work in stream subscriptions

[daviddawson]

Permit active active by distributing event processing around the active members.

Implement using a hash bucket/ hash ring scheme so that each node can individually decide to process. May require tracking stream indeces on a hash bucket basis rather than per stream.

Need to consider hash bucket failover and how scaling up/ down should work. Probably defineany buckets and distribute the evenly, although need to ensure obly 1 sub is active per node, rather than per bucket.