Code freeing can happen at any point in time where a GC might be
triggered. Hence it's difficult to ensure that no other
{CodeSpaceWriteScope} is already open at that point. The way these scope
objects are implemented forbids multiple scopes for different modules
though.
To solve this, this CL just avoids the code zapping in
{WasmCodeAllocator::FreeCode}, which is the only place that actually
writes to the code space. Without this, we do not need the
{CodeSpaceWriteScope} in {NativeModule::FreeCode} any more.

R=jkummerow@chromium.org

Bug: v8:11974
Change-Id: I1f01979e1eaea6c311c9ad568d605aabeef3bfc4
Reviewed-on: https://chromium-review.googlesource.com/c/v8/v8/+/3081522
Commit-Queue: Clemens Backes <clemensb@chromium.org>
Reviewed-by: Jakob Kummerow <jkummerow@chromium.org>
Cr-Commit-Position: refs/heads/master@{#76174}