Reland "Remove references to BindingBase.window (#122119 & #122341)"

* Revert "Remove references to BindingBase.window (#122119)"

This reverts commit c7681f00.

* Revert "Remove another reference to BindingBase.window (#122341)"

This reverts commit 6ec44450.

* Revert "Reland (2): Removes single window assumptions from `flutter_test` (#122233)"

This reverts commit eb3d317e.

* Revert "Remove single view assumption from TestViewConfiguration (#122352)"

This reverts commit 927289fb.

* Revert "Updates `flutter/test/cupertino` to no longer use `TestWindow` (#122325)"

This reverts commit 67e17e45.

* Revert "Updates `flutter/test/gestures` to no longer reference `TestWindow` (#122327)"

This reverts commit c2a5111c.

* Revert "Updates `flutter/test/rendering` to no longer use `TestWindow` (#122347)"

This reverts commit 28b65e08.

* Revert "Updates `flutter_localizations/test` to stop using `TestWindow` (#122321)"

This reverts commit 01367d52.

Remove references to BindingBase.window

The stocks example app is outdated and deprecated, but we still use it for some benchmark tests. Moving it into the benchmarks directory to indicate its status.