Automate Publication of New GKE Marketplace Images to GCR Registry

Overview

There is a Kubernetes-based listing of GitLab on GCP. The listing does not get automatically updated when a new version of GitLab is available. As of Nov 2019 the listing is 11.9.6. The listing should always be the latest version of GitLab so that users can make full use of the newest features in GitLab

Solution

Use the tooling created in #1041 (closed) and automate the publication of validated deployer images to the pre-deployment GitLab registry for Google Marketplace.