[#61991106] Add methadone

This is adding methadone functionality to walker.

You have seen this PR before - the changes I have made are wrt to the comment Sneha made for clarify the code.

The result of this is that you instead of `bundle exec thor vcloud_walk:vdcs` you can now type `bundle exec vcloud-walker vdcs`.

This PR doesn't remove Thor - I thought I would save that for another PR so this one doesn't get too large. So at the moment, both work.