orb-slot-ctrl: Prettify handling of arguments from user

[AlexKaravaev]

Noticed that parsing of status command is a bit clunky, so improved it a bit. I wanted to also add tests for this in this module, but writing tests for cli will require some more refactoring for this file, so I didn't bothered

[AlexKaravaev]

Thanks for the contribution! I also agree that using a dedicated type makes more sense. Two small requested changes and should be good to go.

I've also added clap parsing for Slot

[TheButlah]

@AlexKaravaev can you close or bring up to date?