Drag n drop steps between all lists in a workflow

[ryanhopperlowe]

As of right now, you can only drag-sort elements in the same list. It would be nice to allow users to drag steps between all lists/sublists within the workflow. This will require some research and will likely be non-trivial to implement, but I've confirmed that our library (dnd-kit) does support multiple/nested lists.

A POC that will be very helpful for implementing mutliple/nested lists:
https://www.youtube.com/watch?v=RG-3R6Pu_Ik

[ryanhopperlowe]

@cjellick - assigning you so you can prioritize.