`defang cert generate` in gcp points to `<something>.defang.app` domain

[raphaeltm]

I don't like having <something>.defang.app as the domain defang points to. That creates a dependency on something owned by Defang, which isn't ideal. As a user, part of the benefit of Defang vs other solutions is that it generates nice, self-contained infra in my cloud account. This external dependency breaks that.

Ideally defang cert generate should print the load balancer's static IP address that we can use in an A record.

[edwardrf]

cert gen does not actually do anything except printing out instructions how to setup the DNS, we should update the instructions to display BOTH:

1. xxx.defang.app
2. static IP address for URL map
   And possibly what benefits it brings