Dogfooding the Kubernetes executor - Step 1 - Deploy a cluster on GKE

The first step from #36842 (closed)

• We should deploy an OpenShift cluster and a Kubernetes executor in it
• We should start migrating tests to run on top of that Cluster and Runner

Note: This is important because with #36951 (comment 2040820697)+s done we will have no good way to gauge the completeness of the feature as well as the best direction it should take in the future. Dogfooding is the best way for us to develop the Kubernetes executor further.

Note 2: It should be an OpenShift cluster because we should use the GitLab Runner Operator to deploy the Runner, thus dogfooding even more.

Note 3: As a part of this issue we should gauge whether deploying an OpenShift cluster would be significantly harder than Kubernetes. Maybe we can deploy the Operator in a Kubernetes cluster with OLM.