Our existing implementation of stream piping was extremely ad-hoc. It
did nothing to handle closed/errored streams, and did not read from or
write to streams in a way required by the spec.
This new implementation uses a custom JS::Cell to drive the read/write
loop.
Required by the server-side rendering mode of React Router, used by
https://chatgpt.com/
Note that the imported tests do not have the worker variants to prevent
freezing on macOS.
