Stack list-dependencies : Bring it under the new ls umbrella command

[psibi]

This PR introduces new ls umbrella sub-command. list-dependencies needs to be brought as dependencies under ls.

Do you folks think, we can remove the existing list-dependencies or just deprecate it for the current time being ?

Also I'm assigning the issue to myself, if someone else wants to pickup and do - please let me know. (Edit: It seems I can't assign the issue to myself!)

[borsboom]

I think deprecate it for one major version cycle (e.g. keep with deprecation warning in v1.7 and then remove in v1.8), since it's possible people are using this in automation.