There's no need for them to be in NativeContext.

This CL moves the minimal subset of SFIs related to async iterators.

Bug: v8:10482
Change-Id: I80a34a886387398e6565afe77ab99f389d2ccabd
Reviewed-on: https://chromium-review.googlesource.com/c/v8/v8/+/2184233Reviewed-by: Igor Sheludko <ishell@chromium.org>
Reviewed-by: Michael Lippautz <mlippautz@chromium.org>
Commit-Queue: Marja Hölttä <marja@chromium.org>
Cr-Commit-Position: refs/heads/master@{#67636}