allow advanced props in `dash.callback`

I vaguely remember that Chris might have mentioned this before (if so please link issue), but it would be nice if in dash.callback(id, props) we can use some advanced structure for props. E.g.

@dash.callback(Output(...), Input(my_component.id, ["children", "id"]))
def func(lst):
  print(lst[0])  # => the content of children
  print(lst[1]) # => the ID

Or a dictionary could also work:

@dash.callback(Output(...), Input(my_component.id, {"foo": "children", "bar": "id"}))
def func(di):
  print(di['foo'])  # => the content of children
  print(di['bar']) # => the ID

The issue names dash.callback and Input as the entry points, but does not identify files or tests. Start by tracing how Input props are handled; done would mean supporting the requested list or dictionary prop structures and passing the corresponding values to the callback.