Hosting redis sidekiq on GKE or a non-omnibus deployment using chef

This is a discussion issue from #2818 (comment 1776482093).

For the new Sidekiq shard's redis instance, we are leaning away from using omnibus-gitlab as seen from the difficulties in maintainability (#2754 (comment 1747444979)).

The 2 options are

1. GKE
2. Chef-based deployment using a cookbook like gitlab-redis-cluster for Redis + Sentinels.