Whether to transition between navigation bars.
When transitionBetweenRoutes is true, this navigation bar will transition on top of the routes instead of inside it if the route being transitioned to also has a CupertinoNavigationBar or a CupertinoSliverNavigationBar with transitionBetweenRoutes set to true.
This transition will also occur on edge back swipe gestures like on iOS
but only if the previous page below has
maintainState set to true on the
When set to true, only one navigation bar can be present per route unless heroTag is also set.
This value defaults to true and cannot be null.
final bool transitionBetweenRoutes