edgedb cloud login should be able to print the URL to authenticate with

[msullivan]

I was trying to log in on a remote machine, and had to source dive and then use RUST_LOG=debug to make it work.

[1st1]

yeah, just like edgedb ui.

[mmastrac]

@dnwpark While we're in here, let's aggregate all of the URL-opening code -- I believe there are 2-3 implementations of it scattered around the codebase.