devx: add 1pass (`op`) check to `sg setup`

Created by: courier-new

See https://github.com/sourcegraph/sourcegraph/pull/36340#issuecomment-1197586295.

sg setup has a check that the user has gcloud configured properly. It should probably also have the same check for op. The sg rfc namespace of commands fail with ambiguous errors that don't suggest running sg setup or another actionable solution if op is not set up.