Deploy ratelimiting cluster to nonprod

Milestone goals:

• Prerequisite client compatibility.
  • Any current cross-slot commands are detectable (and any similar future cross-slot commands will be discoverable).
  • Clients do not send cross-slot commands to cluster nodes. Instead, they either use hash tags to colocate keys into a single hash slot or split the commands by hash slot.
• Build and deploy the ratelimiting cluster in nonprod.
  • Iterate on any uncovered issues.
  • Practice reverting the migration back to the old non-cluster Redis instance.
• Dashboards are available for monitoring the cluster's resource usage and SLIs.
  • This may include multiple scopes: the cluster as a whole, its shards ("replica sets"), and its nodes.