Sort busses in new-aux menu by presentation-info

https://discourse.ardour.org/t/ordenation-for-aux-send-buses/112251

libs/ardour/session.cc

@@ -4345,6 +4345,8 @@ Session::get_routes_with_internal_returns() const
 			rl->push_back (i);
 		}
 	}
+
+	rl->sort (Stripable::Sorter ());
 	return rl;
 }