Cleanup clap argument group

[klnusbaum]

Right now, the coupling between the Arg group "action" and the two actions is loose. If we change the name for the arg group, we have to then change the group name for both the args. It'd be better if the name were just in one place. Ideally, we'd have something like what is outlined in clap-rs/clap#2621. Let's wait for that to land.