The intention is to be restrictive for now: modules should not
start to depend on this subtyping while the stringref type
hierarchy question is being settled (see
https://github.com/WebAssembly/stringref/issues/3 for details).

Bug: v8:12868
Change-Id: I0140e72f92550c88393dc84bb1fa3ce65840a048
Reviewed-on: https://chromium-review.googlesource.com/c/v8/v8/+/3865019
Commit-Queue: Matthias Liedtke <mliedtke@chromium.org>
Reviewed-by: Jakob Kummerow <jkummerow@chromium.org>
Cr-Commit-Position: refs/heads/main@{#82937}