Add support for service discovery.

The newly-released Service Discovery framework gives us the interesting
opportunity to make RediStack aware of complex service discovery tools.
This patch supplies a simple adaptor to integrat Service Discovery with
RediStack's pooled client, allowing users to work with arbitrary service
discovery systems.
7 jobs for cb-service-discovery in 4 minutes and 32 seconds (queued for 3 minutes and 31 seconds)
Status Job ID Name Coverage
  Platform Tests
passed Amazon Linux 2

passed CentOS 7

passed CentOS 8

passed Ubuntu Bionic

passed Ubuntu Focal

passed Ubuntu Xenial

  Quality Checks
passed #1049267063
Code Climate