Enable the use of Redis to cache database repository objects

Context

In #452 (closed) we began using an in memory cache for database repository objects. While this has advantages even in a clustered environment, using Redis would allow clustered instances to share a single cache, increasing the cache hit rate.

Implementation plan

This issue will be for the implementation in the Container Registry code.

In Setup a Redis cluster for Registry on Kubernetes (gitlab-com/gl-infra&619 - closed) we will track the Infra work