As part of #114700, an opportunity showed up to unify/clean up the multiple window global objects into a unified API to pass configuration from JS to the engine.

We should attempt to unify all the global configuration entrypoints into the same API, so all the data passed from JS ends up in the engine as part of the configuration FlutterConfiguration object. See configuration.dart.

Docs

• See: (Stretch) Unify JS Configuration section in the design doc