stream: simpler and faster Readable async iterator

Reimplement as an async generator instead of a custom
iterator class.

PR-URL: https://github.com/nodejs/node/pull/34035


Reviewed-By: Matteo Collina <matteo.collina@gmail.com>
Reviewed-By: Benjamin Gruenbaum <benjamingr@gmail.com>
Reviewed-By: James M Snell <jasnell@gmail.com>