once we require Go 1.19 or later, tell go list -json what fields we need

[mvdan]

As an optimization, as otherwise go list -json will need to compute and fill all fields for us. See golang/go#29666.

I don't expect this will be a huge win, but we might as well. This is a reminder for the future when we drop support for Go 1.18, likely in a year or so.