Provision redis-cluster-cache in gstg

Using https://gitlab.com/gitlab-com/runbooks/-/blob/master/docs/redis/provisioning-redis-cluster.md with

• ENV = gstg
• INSTANCE_TYPE=RAILS_INSTANCE_NAME=RAILS_INSTANCE_NAME_OMNIBUS=cache

MRs

• add new chef roles: https://gitlab.com/gitlab-com/gl-infra/chef-repo/-/merge_requests/3626
• infra provisioning via terraform: https://ops.gitlab.net/gitlab-com/gl-infra/config-mgmt/-/merge_requests/6003
• configuring rails in k8s-workload (to be done after load secrets into vault for rails k8s): gitlab-com/gl-infra/k8s-workloads/gitlab-com!2810 (merged)
• updating pre-base.json for console connection: https://gitlab.com/gitlab-com/gl-infra/chef-repo/-/merge_requests/3655

SRE tasks

• create secrets -- https://gitlab.com/gitlab-com/runbooks/-/blob/master/docs/redis/provisioning-redis-cluster.md#1-generate-redis-passwords
• load secrets into vault for rails k8s -- https://gitlab.com/gitlab-com/runbooks/-/blob/master/docs/redis/provisioning-redis-cluster.md#2-configure-gitlab-rails
• To be done togther: load secrets into vault for omnibus + updating pre-base.json for console connection

Admin

• Create CR of ChangeC4