Add Registry integration with CDN scenario

This MR includes changes that enable to:

• Use the Container Registry with a middleware which redirects blob download requests to Google Cloud CDN using pre-signed URLs
• Update the existing configured scenario for Google Cloud Storage as an object storage backend

Observations

• These variables will be made available in 1Password GitLab QA Vault
• GOOGLE_CDN_JSON_KEY and GOOGLE_JSON_KEY could not necessarily store the same key so it is best to have two distinct variables

Resources

To enable these two scenarios, an allocation of resources were made on the gitlab-qa-resources GCP:

• 1 Load Balancer
• 1 static IP
• 1 backend bucket CDN-enabled test-cdn-registry-feature (exclusive for the Registry middleware)
• 1 cloud storage bucket test-object-storage-20210908 (for all GCS Object Storage tests)