Add support for Cupertino widgets and all the adaptive widgets

[EchoEllet]

  localizationsDelegates: const [
        DefaultCupertinoLocalizations.delegate,
        DefaultMaterialLocalizations.delegate,
        DefaultWidgetsLocalizations.delegate,
        FluentLocalizations.delegate,
      ],

when using FluentApp.

Before:

After:

Pre-launch Checklist

• I have updated CHANGELOG.md with my changes
• I have run "dart format ." on the project
• I have added/updated relevant documentation

[bdlukaa]

You may need to rebase

[EchoEllet]

Hi again, You might want to consider replying to this suggestion if possible:

Why we are not using the ScrollBar (material version) widget as default for Android and Fuchsia OS??

[bdlukaa]

Please take a look at scroll_pos change log
it has a breaking change

#947 has fixed this. Please revert

[EchoEllet]

Please take a look at scroll_pos change log
it has a breaking change

#947 has fixed this. Please revert

Done