dillon1000/react

[Flight / Flight Reply] Encode Iterator separately from Iterable (#28854)

For [`AsyncIterable`](https://github.com/facebook/react/pull/28847) we
encode `AsyncIterator` as a separate tag.

Previously we encoded `Iterator` as just an Array. This adds a special
encoding for this. Technically this is a breaking change.

This is kind of an edge case that you'd care about the difference but it
becomes more important to treat these correctly for the warnings here
#28853.