GitLab.com Container Registry to use Google Cloud CDN

What this post added

This post details the integration of Google Cloud CDN with the GitLab.com Container Registry. The change redirects download requests for blobs from Google Cloud Storage to Google Cloud CDN (`cdn.registry.gitlab-static.net`) to optimize costs and improve performance, especially for GitLab CI users. Requests originating from within GCP will continue to use Cloud Storage. The rollout will be gradual, starting in late January 2022, and users who allow-list `storage.googleapis.com` will need to add `cdn.registry.gitlab-static.net`.