Also a couple of microoptimizations and consistent formatting in
WriteToFlat.

Change-Id: Ie642a4b8e0819b04603ee5c5d12eebccf6a2d59c
Reviewed-on: https://chromium-review.googlesource.com/c/v8/v8/+/3151963
Commit-Queue: Leszek Swirski <leszeks@chromium.org>
Reviewed-by: Jakob Gruber <jgruber@chromium.org>
Reviewed-by: Igor Sheludko <ishell@chromium.org>
Cr-Commit-Position: refs/heads/main@{#76799}