Return the predictable preview URL in the preview action

[gadkins]

Currently we return the deployment URL (e.g. https://app.uffizzi.com/projects/5204/deployments/18012/containers) in the "Deploy New Preview" step of the reusable workflow. However, if someone visits this URL while the preview is i progress or after it's been deleted, they will see a 503 or 404.

If we return the predictable preview URL instead, they will be served a custom "Preview in progress..." or "Preview was deleted" page. This makes for a better UX