Expand/collapse the list of values in the group by and color by panels

## Use Case

Requested by @MFarhadloo25. Majid would like to be able to collapse the list of feature values in the Color by and Group by panels.

## Solution

- [ ] Add a collapsible section where the features list currently is.

## Alternatives

Unclear how it would interact with the current show/hide all controls... would they need to be indented in another layer?