Deploy cert-manager to managed cluster for SSL certificates

What does this MR do?

Adds Cert-Manager application to GitLab 1-click deploy.

Note: For cert-manager to work with ingresses (e.g. our JupyterHub deployment), the ingress needs additional TLS section. That should be handled as a separate MR. But I have tested those changes manually and it does generate proper certificate and serves Jupyter over HTTPS. See steps for it below.

Note: This is WIP MR. Tests etc. are remaining.

How did I test this?

I tested it with Jupyter Ingress (steps below). @DylanGriffith and @tkuah are going to help QA this for AutoDevOps application. Ultimately any app deployed via Gitlab's K8s Cluster should be accessible over HTTPS.

• Verify that your Gitlab user's email address is real (and not admin@example.com etc.). Let's Encrypt doesn't allow example.com and other fake emails.
• Create cluster & one click install Helm, Ingress, Cert-Manager, and Jupyter.
• Go to GKE console -> Your cluster -> Services -> JupyterHub Ingress. Click edit and add TLS section (as shown in picture), also add the annotation kubernetes.io/tls-acme: "true" (as shown in same picture).
• Hit save. You should see certificate created under the events tab and Jupyter endpoint accessible via HTTPS.

What are the relevant issue numbers?

• https://gitlab.com/gitlab-org/gitlab-ce/issues/40635

Does this MR meet the acceptance criteria?

• Changelog entry added, if necessary
• Documentation created/updated
• Tests added for this feature/bug
• Conforms to the code review guidelines
• Conforms to the merge request performance guidelines
• Conforms to the style guides
• Conforms to the database guides
• Link to e2e tests MR added if this MR has Requires e2e tests label. See the Test Planning Process.