Some of the fields come from MapRef calls and we have to still serialize
them while Map is bg-serialized. An alternative would be to move them to
MapData but that comes with a cost since different maps with the same
descriptor array wouldn't share said data.

Bug: v8:7790
Change-Id: I25d8eaf7b0a8bf7de0f21272cc6f86cc172b8b08
Reviewed-on: https://chromium-review.googlesource.com/c/v8/v8/+/3008640
Commit-Queue: Santiago Aboy Solanes <solanes@chromium.org>
Reviewed-by: Jakob Gruber <jgruber@chromium.org>
Cr-Commit-Position: refs/heads/master@{#75936}