Enable a clang warning that embedders might enable, and fix issues
found by it.

R=ahaas@chromium.org, nicohartmann@chromium.org, mlippautz@chromium.org

Bug: v8:13069
Change-Id: I935f18872178f4421b441f33ef8ab1d8f030dfc6
Reviewed-on: https://chromium-review.googlesource.com/c/v8/v8/+/3760443Reviewed-by: Michael Achenbach <machenbach@chromium.org>
Reviewed-by: Nico Hartmann <nicohartmann@chromium.org>
Reviewed-by: Michael Lippautz <mlippautz@chromium.org>
Reviewed-by: Andreas Haas <ahaas@chromium.org>
Commit-Queue: Clemens Backes <clemensb@chromium.org>
Cr-Commit-Position: refs/heads/main@{#81853}