Provision redis-cluster-ratelimiting in gstg

This was previously done in pre as part of #2011 (closed).

We now want to roll out to gstg as it has a more regular deploy cadence than pre and thus makes it easier for us to iterate.

Requirements:

• Set up chef role: https://gitlab.com/gitlab-com/gl-infra/chef-repo/-/merge_requests/2930
• Set up prometheus scraping: https://gitlab.com/gitlab-com/gl-infra/chef-repo/-/merge_requests/2934
• Set up GKMS secrets
• Create nodes in terraform: https://ops.gitlab.net/gitlab-com/gl-infra/config-mgmt/-/merge_requests/5052
• Initialize redis cluster
• Set up secrets in hashicorp vault
• Configure rails clients to talk to this cluster in gstg: gitlab-com/gl-infra/k8s-workloads/gitlab-com!2571 (merged)