Use concurrency-limits for adaptive query processing admission queue sizing #8357

Druid's Historicals, Indexing Peons, Brokers, and Routers could leverage https://github.com/Netflix/concurrency-limits to auto-tune query queue size. See this blog post for the explanation.

concurrency-limits library is one of the successors (along with resilience4j) of Netflix Hystrix which was previously brought to the community attention here and here by @sashidhar. However, Hystrix is now in the maintenance mode so if Druid was to adopt any of these libraries, they should be concurrency-limits and/or resilience4j rather than Hystrix.

This issue is somewhat related to #8356.