Allow other queues to be fed

[DiegoPino]

What is this?

This came from a friendly talk I had today. For larger deployments the internal Drupal queues may not be scaleable enough, or said differently, we may have macro queues feeding the Drupal Worker driven ones. The need is simple to accomplish. I will add a queue service that can be extended via plugins to feed others/too/instead and then we can figure out if an AWS/rabbit to even a RocksDB one can be added as recipient for pending processes as external services.

[DiegoPino]

Note for myself @DiegoPino:
REDIS is bad for large persisting Queues. In an experimental setting, with slow ingesting queues because the site is not public and Cron was set to every few days, the SBR (e.g OCR) queue grew to 500K from a total of 30K objects (15 pages per PDF?). That in memory (redis) became 11 Gbytes.