dillon1000/react

Serialize Promises through Flight (#26086)

This lets you pass Promises from server components to client components
and `use()` them there.

We still don't support Promises as children on the client, so we need to
support both. This will be a lot simpler when we remove the need to
encode children as lazy since we don't need the lazy encoding anymore
then.

I noticed that this test failed because we don't synchronously resolve
instrumented Promises if they're lazy. The second fix calls `.then()`
early to ensure that this lazy initialization can happen eagerly. ~It
felt silly to do this with an empty function or something, so I just did
the attachment of ping listeners early here. It's also a little silly
since they will ping the currently running render for no reason if it's
synchronously available.~ EDIT: That didn't work because a ping might
interrupt the current render. Probably need a bigger refactor.

We could add another extension but we've already taken a lot of
liberties with the Promise protocol. At least this is one that doesn't
need extension of the protocol as much. Any sub-class of promises could
do this.