Runtime APIs: MessageChannel

The [MessageChannel](https://developer.mozilla.org/en-US/docs/Web/API/MessageChannel) API is available on [node](https://nodejs.org/api/worker_threads.html#class-messagechannel) but not CF Workers. This is causing an issue during the deployment of sites using React 19 + Astro + Workers, see https://github.com/facebook/react/issues/31827 and https://github.com/withastro/astro/issues/12824. The _usage_ of this API may be a bug for this use case (meaning the solution there may be to stop using MessageChannel), but workerd may want to support it anyway.

I made a repository with steps to reproduce the crash mentioned in those issues here: https://github.com/phase/test-astro-react19-cf-workers