The byte_length of ArrayBuffers may be a heap number. This length is
needed for freeing a buffer during tear down, implying that ArrayBuffers
need to be freed before regular space tear down can remove actual pages.

Bug: v8:7623
Change-Id: Iab91843e48c50276a2e110915f69cf9e6c24ef8f
Reviewed-on: https://chromium-review.googlesource.com/997776
Commit-Queue: Michael Lippautz <mlippautz@chromium.org>
Reviewed-by: Hannes Payer <hpayer@chromium.org>
Cr-Commit-Position: refs/heads/master@{#52426}