Also:
* Remove forward declare and As##Name for never serialized Data classes
* Remove the Data classes
* Refactor macro list to encode being background or never serialized

Bug: v8:7790
Change-Id: Ide29d89072b247311f29948f04c4147c5c1103cc
Reviewed-on: https://chromium-review.googlesource.com/c/v8/v8/+/3056458
Commit-Queue: Santiago Aboy Solanes <solanes@chromium.org>
Reviewed-by: Jakob Gruber <jgruber@chromium.org>
Cr-Commit-Position: refs/heads/master@{#76032}