Merging typed slots in the marking barrier may require allocating a
new typed slots set. We need a CodePageHeaderModificationScope since
that slot set is actually written into the code page.

Bug: chromium:1336850, v8:12797
Change-Id: If3f7d2bb179c2554ea2888c5ad92f098bd29b1c5
Reviewed-on: https://chromium-review.googlesource.com/c/v8/v8/+/3751210Reviewed-by: Igor Sheludko <ishell@chromium.org>
Commit-Queue: Michael Lippautz <mlippautz@chromium.org>
Cr-Commit-Position: refs/heads/main@{#81590}