Fix T82588: Box Select selects keyframes hidden by "Only Show Selected"

Select only editable keys on selected curves when "Only Show Selected
Curves" is enabled in the Graph Editor's View menu.

This prevents selecting invisible keys with box, circle, and lasso
select in the Graph Editor.

Reviewed By: looch

Differential Revision: https://developer.blender.org/D9580

source/blender/editors/space_graph/graph_select.c

@@ -529,6 +529,9 @@ static void box_select_graphkeys(bAnimContext *ac,
 
   /* filter data */
   filter = (ANIMFILTER_DATA_VISIBLE | ANIMFILTER_CURVE_VISIBLE | ANIMFILTER_NODUPLIS);
+  if (sipo->flag & SIPO_SELCUVERTSONLY) {
+    filter |= ANIMFILTER_FOREDIT | ANIMFILTER_SELEDIT;
+  }
   ANIM_animdata_filter(ac, &anim_data, filter, ac->data, ac->datatype);
 
   /* get beztriple editing/validation funcs  */