Refactor the PromiseHandle builtin and move the separate debug checks
into the PromiseHookBefore and PromiseHookAfter runtime calls, so they
are performed only when we've already hit the slow-path.

Bug: v8:7253
Change-Id: I01ab8592a474b6897280734b995cab0b90a5e010
Reviewed-on: https://chromium-review.googlesource.com/884583Reviewed-by: Sathya Gunasekaran <gsathya@chromium.org>
Commit-Queue: Benedikt Meurer <bmeurer@chromium.org>
Cr-Commit-Position: refs/heads/master@{#50856}