## Description
This factors out a separate `RawView` that doesn't add a `MediaQuery` or a `FocusScope`. This PR also adds a new method `WidgetsBindingObserver.didChangeViewFocus` which allows the observer to know when the `FlutterView` that has focus has changed.
It also makes the `View` widget a stateful widget that contains a `FocusScope` and ` FocusTraversalGroup` so that it can respond to changes in the focus of the view.
I've also added a new function to `FocusScopeNode` that will allow the scope node itself to be focused, without looking for descendants that could take the focus. This lets the focus be "parked" at the `FocusManager.instance.rootScope` so that nothing else appears to have focus.
## Tests
- Added tests for the new functionality.
* Adds `TestDisplay`
* Updates `TestPlatformDispatcher` to wrap all `Display`s and relate them to their appropriate `TestFlutterView`
* Updates `TestFlutterView` to tie `devicePixelRatio` to its display as per the documentation on `Display`
Closes#127225
* Revert "Remove references to BindingBase.window (#122119)"
This reverts commit c7681f00cf.
* Revert "Remove another reference to BindingBase.window (#122341)"
This reverts commit 6ec4445063.
* Revert "Reland (2): Removes single window assumptions from `flutter_test` (#122233)"
This reverts commit eb3d317ea0.
* Revert "Remove single view assumption from TestViewConfiguration (#122352)"
This reverts commit 927289fb4e.
* Revert "Updates `flutter/test/cupertino` to no longer use `TestWindow` (#122325)"
This reverts commit 67e17e45f0.
* Revert "Updates `flutter/test/gestures` to no longer reference `TestWindow` (#122327)"
This reverts commit c2a5111cc0.
* Revert "Updates `flutter/test/rendering` to no longer use `TestWindow` (#122347)"
This reverts commit 28b65e089b.
* Revert "Updates `flutter_localizations/test` to stop using `TestWindow` (#122321)"
This reverts commit 01367d52d7.
