Without this fix, the byte length for GSABs is probably serialized
wrong. A failing test is omitted since it would be pretty involved
(currently this code path is only hit with --stress-snapshot).

Bug: v8:11111
Change-Id: If7df98263cec9f82766c2fa6ba095b98b53a6fde
Reviewed-on: https://chromium-review.googlesource.com/c/v8/v8/+/3657431Reviewed-by: Leszek Swirski <leszeks@chromium.org>
Commit-Queue: Marja Hölttä <marja@chromium.org>
Reviewed-by: Jakob Kummerow <jkummerow@chromium.org>
Reviewed-by: Shu-yu Guo <syg@chromium.org>
Cr-Commit-Position: refs/heads/main@{#80780}