A folded allocation must fit into a regular (= non-large-object) heap
space. This CL changes AsyncFunctionEnter to allocate the
variable-sized fixed array separately from the folded JSPromise and
JSAsyncFunctionObject.

Bug: v8:9398
Change-Id: I9f3642e0bf060f7b61a42d6f490adbbb6d753ac6
Reviewed-on: https://chromium-review.googlesource.com/c/v8/v8/+/1684000
Auto-Submit: Jakob Gruber <jgruber@chromium.org>
Commit-Queue: Benedikt Meurer <bmeurer@chromium.org>
Reviewed-by: Benedikt Meurer <bmeurer@chromium.org>
Cr-Commit-Position: refs/heads/master@{#62476}