Fix #66286: DblClick to rename UIList items within a popover not working

Looks like most of `ui_apply_but_XXX` or `ui_do_but_XXX` functions rely
on `uiHandleButtonData` (and not necessarily context).

Now the problem from a popover in `ui_but_list_row_text_activate` was
that the label button to be set in BUTTON_ACTIVATE_TEXT_EDITING for
renaming could not be found because it was using the "wrong" region from
context (`CTX_wm_region` - which still seem to point to the region the
popover was spawned from). The correct region is available in
`uiHandleButtonData` though, so now use this instead.

Not totally sure if `CTX_wm_region` should actually be correct in all
cases - which would hint at an underlying problem of not setting it
right - but since other functions rely on `uiHandleButtonData` as well,
this fix seems to make sense.

Fix should go into LTS I think.

Pull Request: https://projects.blender.org/blender/blender/pulls/114363

source/blender/editors/interface/interface_handlers.cc

@@ -4412,7 +4412,7 @@ static uiBut *ui_but_list_row_text_activate(bContext *C,
                                             const wmEvent *event,
                                             uiButtonActivateType activate_type)
 {
-  ARegion *region = CTX_wm_region(C);
+  ARegion *region = data->region;
   uiBut *labelbut = ui_but_find_mouse_over_ex(region, event->xy, true, false, nullptr, nullptr);
 
   if (labelbut && labelbut->type == UI_BTYPE_TEXT && !(labelbut->flag & UI_BUT_DISABLED)) {