Since db6287873c, we added parenting (Keep Transform Without Inverse)
to the parent_set operator and exposed this in the UI in the invoke menu
of that operator.
This however never made it to the `Object` > `Parent` menu.
Since this is quite useful (and otherwise a bit hidden in the Adjust
Last Operation panel) and parent inverse can cause confusion in many
cases (see e.g. #105276 or #103969), now add this as an explicit entry
in the `Object` > `Parent` menu as well.