WM: use pass-through for cursor placement operator

This is needed since 4d0f846b93
however change in the operator instead of the event handler is correct,
as accepting a press event should suppress drag events unless
the pass-through flag is set.

This is how select & tweak already works.

source/blender/editors/space_clip/clip_ops.c

@@ -1779,7 +1779,8 @@ static int clip_set_2d_cursor_exec(bContext *C, wmOperator *op)
 
   WM_event_add_notifier(C, NC_SPACE | ND_SPACE_CLIP, NULL);
 
-  return OPERATOR_FINISHED;
+  /* Use pass-through to allow click-drag to transform the cursor. */
+  return OPERATOR_FINISHED | OPERATOR_PASS_THROUGH;
 }
 
 static int clip_set_2d_cursor_invoke(bContext *C, wmOperator *op, const wmEvent *event)

source/blender/editors/space_sequencer/sequencer_edit.c

@@ -3510,7 +3510,8 @@ static int sequencer_set_2d_cursor_exec(bContext *C, wmOperator *op)
 
   WM_event_add_notifier(C, NC_SPACE | ND_SPACE_SEQUENCER, NULL);
 
-  return OPERATOR_FINISHED;
+  /* Use pass-through to allow click-drag to transform the cursor. */
+  return OPERATOR_FINISHED | OPERATOR_PASS_THROUGH;
 }
 
 static int sequencer_set_2d_cursor_invoke(bContext *C, wmOperator *op, const wmEvent *event)

source/blender/editors/space_view3d/view3d_edit.c

@@ -1063,7 +1063,8 @@ static int view3d_cursor3d_invoke(bContext *C, wmOperator *op, const wmEvent *ev
   const enum eV3DCursorOrient orientation = RNA_enum_get(op->ptr, "orientation");
   ED_view3d_cursor3d_update(C, event->mval, use_depth, orientation);
 
-  return OPERATOR_FINISHED;
+  /* Use pass-through to allow click-drag to transform the cursor. */
+  return OPERATOR_FINISHED | OPERATOR_PASS_THROUGH;
 }
 
 void VIEW3D_OT_cursor3d(wmOperatorType *ot)

source/blender/editors/uvedit/uvedit_ops.c

@@ -1739,7 +1739,8 @@ static int uv_set_2d_cursor_exec(bContext *C, wmOperator *op)
 
   WM_event_add_notifier(C, NC_SPACE | ND_SPACE_IMAGE, NULL);
 
-  return OPERATOR_FINISHED;
+  /* Use pass-through to allow click-drag to transform the cursor. */
+  return OPERATOR_FINISHED | OPERATOR_PASS_THROUGH;
 }
 
 static int uv_set_2d_cursor_invoke(bContext *C, wmOperator *op, const wmEvent *event)