Add redis-registry-cache service
Part of gitlab-com/gl-infra/scalability#1818 (closed)
The apdex definitions for the registry_redis_client
component are directly taken from the redis
component in the registry
service added on !4909 (merged), but we still want the new redis instance to have its own dashboards and be a first-class service in our catalog.
Snapshot of the new dashboard: https://dashboards.gitlab.net/dashboard/snapshot/Re62gSS6aFxs31tAY2SzVRYE5XiUokxz?orgId=1&var-environment=pre (some metrics missing since they're being added on this commit)