Reimplement CupertinoModalSheetRoute and Page with ModalRoute.delegatedTransition

[fujidaiti]

Finally, the Flutter SDK has introduced an official way to implement the iOS-style stacked modal route transition in version 3.27. Leveraging this feature can simplify the current API of CupertinoModalSheetRoute.

ModalRoutes are now more flexible when the previous and new routes have different page transitions. When a new route enters the screen, sometimes they need the previous existing route to play a certain transition to sync up with the entrance transition of the new route. Now ModalRoutes can provide exit transition builders to each other so the enter and exit transitions always sync up. This allows pages to have multiple route transition options on one page using Flutter’s Navigator and Router.

https://medium.com/flutter/whats-new-in-flutter-3-27-28341129570c#:~:text=Mixing%20Route%20Transitions