[Review Apps] Add resource requests and limits to most of the chart resources

What does this MR do?

1. I noticed that some VM instances (i.e. nodes) were at 100% CPU.
   1. At the same time, I noticed that the gitlab-runner deployment doesn't have resource requests. This is a problem because GCP autoscaling is based on the resource requests, not the actual resource usage (unless it hits the triggers set for the node, e.g. MemoryPressure).
   2. I also noticed that the gitaly and gitlab-shell deployments were using more than their requested resources, which again could lead to non-optimal autoscaling decisions from GCP, leading to degraded Review App deployment timings, or even timeouts.
   • I've decided to specify resources requests and limits for pretty much all the deployments/pods of the chart, based on actual numbers from the deployed Review Apps that we have.

gitaly

gitlab-shell

sidekiq

unicorn

redis

minio

gitlab-runner

gitlab-monitor

postgresql

registry

Does this MR meet the acceptance criteria?

Conformity

• [-] Changelog entry
• Documentation created/updated or follow-up review issue created
• Code review guidelines
• Merge request performance guidelines
• Style guides
• Database guides
• Separation of EE specific content