The V8-side of top-level await is complete.
Staging this feature to get fuzzing coverage.

Bug: chrome:1022182, v8:9344
Change-Id: I1b88d0450aa148b84c62659628d492ffc3074d0f
Reviewed-on: https://chromium-review.googlesource.com/c/v8/v8/+/2185132Reviewed-by: Shu-yu Guo <syg@chromium.org>
Commit-Queue: Camillo Bruni <cbruni@chromium.org>
Cr-Commit-Position: refs/heads/master@{#67697}