Dogfooding the Kubernetes executor - Step 2 - Run Kubernetes integration tests inside the cluster

This issue aims to run the kubernetes integration tests on the k8s cluster deployed with #37988 (closed).

The k3s kubernetes cluster we run inside each job is not dependable, thus we have marked the tests as allowed to fail. This reduces the confidence in the executor.

An example such job is https://gitlab.com/gitlab-org/gitlab-runner/-/jobs/8338359186 where the pods simply will not start.