... but keep/make subclass-specific methods do direct reads.

Bug: v8:7790
Change-Id: Ia4b9d207ce75cf28f6f0f33027ab05e27db49ce9
Reviewed-on: https://chromium-review.googlesource.com/c/v8/v8/+/2959621Reviewed-by: Jakob Gruber <jgruber@chromium.org>
Reviewed-by: Georg Neis <neis@chromium.org>
Commit-Queue: Jakob Gruber <jgruber@chromium.org>
Cr-Commit-Position: refs/heads/master@{#75457}