unified-selection: imodelKey should be optional #1069
Description
Based on https://github.com/iTwin/contextual-tree-control-react/blob/b1df7b65d194d77a59bd73f61cee4468e8922825/packages/scenes-control-react/src/scenes-control-react/shared/Selection.ts#L39-L40 - when unified selection is used outside of iModels' context, we should not be forcing consumers to specify an imodelKey.