Fallback when gc job fails

[zifeo]

If something bad happens within https://github.com/enix/kube-image-keeper/blob/main/helm/kube-image-keeper/templates/garbage-collection-cron-job.yaml, the registry might end up locked forever. A fallback scenario should be provided.

Additionally, the job is using bitnami/kubectl which should maybe also be cached but kuik seems to ignore its namespace.