Trivial changes to the parser to allow parsing for-await. Unfortunately,
these tests uncovered a stress bug related to using await in for
loops(see v8:9825).

Bug: v8:9817, v8:9825
Change-Id: Ie699c85389e94b834a22dc1fb2f9970fc37fcdd3
Reviewed-on: https://chromium-review.googlesource.com/c/v8/v8/+/1848434Reviewed-by: Georg Neis <neis@chromium.org>
Commit-Queue: Joshua Litt <joshualitt@chromium.org>
Cr-Commit-Position: refs/heads/master@{#64193}