Add Production URL option to Site Settings (also option to remove "Deployment")

I’d like to propose two changes which are relevant for projects that are using the API rather than the SSG ‘dump’ workflow:

  1. add the option to hide/remove Deployment Settings (since there may be no build step involved)
  2. add a “Production URL” setting to the Site Settings, which would be the canonical reference for the URL visited when user clicks on the “Visit Site” button. If this option is not configured, but a Production Deployment is configured, then Production URL would fallback to that.