`GroupingChooser` should keep transient UI state separate from the provided model

[haynesjm42]

Currently GroupingChooserModel contains transient UI state, like whether the editor is open or closed. This results in the undesired behavior where if you have multiple groupingChooser components rendered bound to the same model, clicking on one chooser will open the editor in all choosers.

It seems like we should keep transient UI state in a local model for each component so instances like this behave as expected.

I ran into this while using the panel modal support to show a larger version of a widget, so I have 2 grouping choosers rendered sharing the same model.