Save state of the widgets in the NavigationPane

[EchoEllet]

Is your feature request related to a problem? Please describe.
The NavigationPane doesn't save the state of the widget when navigating between different items in the navigation menu and we
have to manually split the state from the UI and use state management packages like provider or flutter_riverpod etc...
and AutomaticKeepAliveClientMixin doesn't work because of the way that NavigationPane works
at least make it works like the way it is in Material UI so we can fix that or make it automatic like Cupertino UI

Describe the solution you'd like
I already did,

Describe alternatives you've considered
Material UI and Cupertino

Additional context
I don't have anything else to say

[thitlwincoder]

I try this. It work for me.

paneBodyBuilder: (item, body) {
  return body!;
},

[bdlukaa]

Assigning a key to the item may also work

[bdlukaa]

You can add an AutomaticKeepAliveMixin mixin to your body widgets. You can also make use of page storage to save the state.

AutomaticKeepAliveClientMixin doesn't work because of the way that NavigationPane works

Recently, NavigationView now uses PageView under the hood to render the body widgets. This enables the usage of AutomaticKeepAliveClientMixin

If you make use of go_router, you can use StatefulShellRoute.

Related #910