When closing a concurrent allocator, for instance when closing a
LocalHeap, we need to make the LAB of the code space iterable.
We add then a CodePageMemoryModificationScope to allow
code space modification.

Bug: v8:12054
Change-Id: I438d7c1a50694930b7558dec2dd552bec22b7552
Reviewed-on: https://chromium-review.googlesource.com/c/v8/v8/+/3277887
Commit-Queue: Victor Gomes <victorgomes@chromium.org>
Reviewed-by: Dominik Inführ <dinfuehr@chromium.org>
Cr-Commit-Position: refs/heads/main@{#77871}