This allows `new (Pretenured) X{}` to force a pretenured allocation.

Bug: v8:7793
Change-Id: Ib09f186b3b503b9b23291c39c1390f120d25eebe
Reviewed-on: https://chromium-review.googlesource.com/c/v8/v8/+/2288409
Commit-Queue: Gus Caplan <me@gus.host>
Reviewed-by: Tobias Tebbi <tebbi@chromium.org>
Cr-Commit-Position: refs/heads/master@{#68801}