Like all metadata areas, the cp offset must be less than the body
size. (In a follow-up, this will change s.t. offsets must be less than
the metadata size.)

Tbr: leszeks@chromium.org
Bug: v8:11036
Change-Id: I108238601f36acd8d22fa161c042d4ca82b07e87
Reviewed-on: https://chromium-review.googlesource.com/c/v8/v8/+/2501281Reviewed-by: Jakob Gruber <jgruber@chromium.org>
Commit-Queue: Jakob Gruber <jgruber@chromium.org>
Cr-Commit-Position: refs/heads/master@{#70781}