This CL is an improvement on
https://chromium-review.googlesource.com/c/v8/v8/+/1664052
which introduced unnecessary boilerplate (now reverted).

The code objects for resolve/reject handlers are builtins, and
therefore already serialized.

R=jarin@chromium.org

Bug: v8:7790
Change-Id: I6a49110aa794d4bd380cabd40e67fba7783e642a
Reviewed-on: https://chromium-review.googlesource.com/c/v8/v8/+/1664055
Commit-Queue: Michael Stanton <mvstanton@chromium.org>
Reviewed-by: Jaroslav Sevcik <jarin@chromium.org>
Cr-Commit-Position: refs/heads/master@{#62236}