LargePage::PayloadSize inclues the heap object header.
Keeping PayloadSize as is to keep it aligned with
NormalPage::PayloadSize and introducing LargePage::ObjectSize as the
counterpart for HeapObjectHeader::ObjectSize that will exclude the
header.

Bug: chromium:1056170
Change-Id: I8a5f50841fd9dbd6c9a4a4035d9040021944cacc
Reviewed-on: https://chromium-review.googlesource.com/c/v8/v8/+/2731533Reviewed-by: Michael Lippautz <mlippautz@chromium.org>
Commit-Queue: Omer Katz <omerkatz@chromium.org>
Cr-Commit-Position: refs/heads/master@{#73154}