A new "Show Cumulative Curve" checkbox on the grid statistics data source adds a cumulative curve on the right axis, in addition to the regular histogram curve. The cumulative curve shares the data source of its non-cumulative counterpart and follows all changes to it. The cumulative sum works with all frequency types and both graph types.
Remove the legacy Grid Statistics dialog (RicGridStatisticsDialog) and its context menu command, which provided the previous cumulative display.
Use QPointer instead of unique_ptr for m_gridStatisticsDialog to avoid double-free when Qt's parent-child mechanism deletes the dialog before Rim3dOverlayInfoConfig destructor runs.