[pre] Enable Redis metadata caching for Container Registry

Now that we've setup the Redis cluster for Container Registry in pre in #1804 (closed), let's configure Registry to connect to it so that we can see the behavior of the components in a deployed environment. Some chart adjustments are needed to accomplish this:

• Add support for redis-cache gitlab-org/charts/gitlab!2675 (merged)
• Support defining a local set of sentinels gitlab-org/charts/gitlab!2729 (merged)

After that we can deploy the configuration changes:

• Enable Redis metadata caching for Container Registry (pre) gitlab-com/gl-infra/k8s-workloads/gitlab-com!2042 (merged)
• Remove custom masterSet gitlab-com/gl-infra/k8s-workloads/tanka-deployments!516 (merged)