This builtin was initially used to create the promise for an async
function, but that is now done by the AsyncFunctionEnter intrinsic.

Bug: v8:7253
Change-Id: I90d0bb31c1548bbfdb53833a5c06161db368f4f0
Reviewed-on: https://chromium-review.googlesource.com/c/1296129Reviewed-by: Yang Guo <yangguo@chromium.org>
Commit-Queue: Benedikt Meurer <bmeurer@chromium.org>
Cr-Commit-Position: refs/heads/master@{#56878}