Nobody uses the generated *_FIELDS macros anymore, so we can remove
them. I also renamed the generated file to represent its content better.

Bug: v8:7793
Change-Id: I49ab39e363d6961e7210cd67018b6fb83b65a162
Reviewed-on: https://chromium-review.googlesource.com/c/v8/v8/+/3192191Reviewed-by: Nico Hartmann <nicohartmann@chromium.org>
Reviewed-by: Dominik Inführ <dinfuehr@chromium.org>
Commit-Queue: Seth Brenith <seth.brenith@microsoft.com>
Cr-Commit-Position: refs/heads/main@{#77151}