Ensure EE Review Apps cluster is big enough (or even autoscaled) and Review Apps are automatically cleaned up after x days

I noticed that Review Apps are not created for EE MRs, and after looking at the Kubernetes console we have the following message:

 Cluster review-apps-ee has unschedulable pods
Problem

Your cluster has 372 unschedulable pods
Details

    Unschedulable pods
    kube-dns-778977457c-qfxqg
    kubernetes-dashboard-6bb875b5bc-429h6
    review-11-1-stabl-amn5zn-gitaly-0
    review-11-1-stabl-amn5zn-gitlab-shell-5bddd94f9f-7brcj
    review-11-1-stabl-amn5zn-gitlab-shell-5bddd94f9f-skgpr
    and other 367 unschedulable pods.

Possible Actions

    Enable Autoscaling in one or more node pools that have autoscaling disabled.
    Increase size of one or more node pools manually.

Autoscaling seems like the best solution here, but we should monitor the costs closely and probably put a limit to how many pods can be spin up in the cluster... /cc @marin