`GridModel.clicksToExpand: 1` not respected for full-width group rows

[amcclain]

GridModel supports a clicksToExpand prop, but it is only applied when treeMode == true. We wanted this to work for a simple grouped grid (full width grouping rows).

(More specifically, we wanted it to apply to a grouped DataView, where the client wants all of the groups to be collapsed by default so the user can see a clean list of categories, but then we want it to be trivial to expand any of those groups to see the actual content w/minimal friction).

Curious if there was a reason that we limited this to treeMode only:

hoist-react/cmp/grid/Grid.ts

Line 849 in 8d79c72

if (!event.defaultPrevented && treeMode && clicksToExpand === 1 && node?.allChildrenCount) {

I also wasn't able to find any native AG Grid option to get this behavior.