UI: Add icons to Set Handle Type menu

Add icons to curves "Set Handle Type" menu, (both legacy Curve and new
Curves). Matching those in the Curve widgets.

Graph Editor already uses icons for that menu.

See PR for details and screenshots.

Pull Request: https://projects.blender.org/blender/blender/pulls/148322

source/blender/editors/curves/intern/curves_ops.cc

@@ -1793,22 +1793,22 @@ static wmOperatorStatus exec(bContext *C, wmOperator *op)
 const EnumPropertyItem rna_enum_set_handle_type_items[] = {
     {int(SetHandleType::Auto),
      "AUTO",
-     0,
+     ICON_HANDLE_AUTO,
      "Auto",
      "The location is automatically calculated to be smooth"},
     {int(SetHandleType::Vector),
      "VECTOR",
-     0,
+     ICON_HANDLE_VECTOR,
      "Vector",
      "The location is calculated to point to the next/previous control point"},
     {int(SetHandleType::Align),
      "ALIGN",
-     0,
+     ICON_HANDLE_ALIGNED,
      "Align",
      "The location is constrained to point in the opposite direction as the other handle"},
     {int(SetHandleType::Free),
      "FREE_ALIGN",
-     0,
+     ICON_HANDLE_FREE,
      "Free",
      "The handle can be moved anywhere, and does not influence the point's other handle"},
     {int(SetHandleType::Toggle),