Running `edgedb instance <subcommand>` in a project

When working in a project, it would be useful to have an easy way to accomplish `edgedb instance -I `.

I propose having `edgedb instance ` implicitly use the instance from the project, since that: aligns with the behavior of running `edgedb`; should not result in unexpected behavior for any of the `instance` subcommands; is likely the most commonly expected behavior.