Upgrade CLI to use Clap v3 over StructOpt #2166
Description
Looks like all the functionality of StructOpt has been added to Clap:
As clap v3 is now out, and the structopt features are integrated into (almost as-is), structopt is now in maintenance mode: no new feature will be added.
Bugs will be fixed, and documentation improvements will be accepted.
Doesn't look too hard: https://github.com/clap-rs/clap#example