Light linking: Use checkbox icons for state indication

This is as per design task #104972

The same icons as exclusion in the outliner are used.

Pull Request: https://projects.blender.org/blender/blender/pulls/112857

source/blender/editors/interface/interface_template_light_linking.cc

@@ -130,12 +130,11 @@ class CollectionViewItem : public BasicTreeViewItem {
  private:
   int get_state_icon() const
   {
-    /* TODO(sergey): Use proper icons. */
     switch (collection_light_linking_.link_state) {
       case COLLECTION_LIGHT_LINKING_STATE_INCLUDE:
-        return ICON_OUTLINER_OB_LIGHT;
+        return ICON_CHECKBOX_HLT;
       case COLLECTION_LIGHT_LINKING_STATE_EXCLUDE:
-        return ICON_LIGHT;
+        return ICON_CHECKBOX_DEHLT;
     }
     BLI_assert_unreachable();
     return ICON_NONE;