Applies #78522 to existing code, by replacing all occurrences of LogicalKeySet to SingleActivator or ShortcutActivator.

Update samples to use repo analysis options, Fix sample templates and a ton of analyzer issues (#77868)

Text editing shortcuts involving the arrow keys are no longer handled by RenderEditable's RawKeyboardListener, they use the new Shortcuts setup.  First PR in a plan to port all text editing keyboard handling to shortcuts.

Remove references to `Window`, and switch usages to `PlatformDispatcher` or `SingletonFlutterWindow` (#69617)

* Remove references to dart:ui.Window, and point usages to PlatformDispatcher or SingletonFlutterWindow, as appropriate

* remove new test platform dispatchers

* Amend documentation

* enable null_check_on_nullable_type_parameter and tighten_type_of_initializing_formals

* fix CI

This reverts commit 81439922.

* migrate some material files to nullsafety

* review

This reverts commit adc5f26b.

This reverts commit 48f1a0a8.

* add language version 2.8 in packages/flutter

* enable non-nullable analyzer flag

This updates the Action API in accordance with the design doc for the changes: flutter.dev/go/actions-and-shortcuts-design-revision

Fixes #53276

This PR adds the linux and windows target platform enum values, along with automatically setting the defaultTargetPlatform to the appropriate value on those platforms.

Fixes #31366

Navigator 2.0: Refactor the imperative api to continue working in the new navigation system (#44930)