Generic NamedQueue framework for recent in-memory history

As per the discussion on parent jira, we should come up with named queue (online ring buffer) to serve recent history for multiple use-cases like slowlog, balancer decision, other region activities e.g flush, compaction, split, merge etc.

Since we already have slow/large rpc logs in ring buffer (HBASE-22978), as part of this Jira, the proposal is to refactor slowlog provider to get generic payload for ring buffer and based on event type (slow_log is the only one for now), we can have separate internal in-memory queues.

After this refactor, it should be relatively simpler to use the same framework and create more cases like parent Jira (balancer decision in ring buffer).