Resurrect The Shape-Chooser menu
One of the things I liked about this plugin originally is that it allowed for me to quickly choose the shapes from a list and bind it to a curve. This was something that was lost when it started to go more towards data paths, and data paths don't come up correctly when you right-click -> "copy data path" from the list of shapes.
Soooo.... I hotwired the list back in.

Choosing other data types not "shapekeys" still accepts data paths, only shapekeys prompts the chooser element. I do currently have the "new shape key" option disabled however (The code to make it work seems to be missing?).
This PR is based off of the non-main 2.8 modernization.
get_prop_obj has a tendency to get very confused, so I updated the branch to take the selected mode into account. Not perfect, not a full conversion, just enough to be more deterministic.