Currently, in multi-view mode, when the user resizes the window, Flutter views don't respond to the resize. This is because `FlutterViewEmbedder` is the one responding to resize events. But `FlutterViewEmbedder` only works with the implicit view, so multi views didn't respond to resize events.
This PR moves the responsibility of responding to resize events from `FlutterViewEmbedder` to `EngineFlutterView`. Also, tests.
Part of https://github.com/flutter/flutter/issues/134443