[pre] Setup a Redis cluster for Registry Cache on Kubernetes

As part of &619, let's setup a Redis cluster on pre for the Container Registry team, and configure it so that it starts being used by that application in that environment.

• Create node pool: https://ops.gitlab.net/gitlab-com/gl-infra/config-mgmt/-/merge_requests/3993
• Provision cluster: gitlab-com/gl-infra/k8s-workloads/tanka-deployments!450 (merged)