{NativeModule::AddCode} is a central method that should usually be
called in batches, where the caller holds a {CodeSpaceWriteScope} for a
longer time (over several compilations).
This CL moves us closer to that by removing the scope from that central
method and instead putting it in callers where it becomes more visible.
There are already TODOs to introduce caching or batching to avoid some
switching, and one more TODO is added.

Drive-by: Remove an unneeded {CodeSpaceMemoryModificationScope}.

R=jkummerow@chromium.org

Bug: v8:11974
Change-Id: Ia13c601abc766e5fca6ca053bf1fc4d647b53ed0
Reviewed-on: https://chromium-review.googlesource.com/c/v8/v8/+/3098186Reviewed-by: Jakob Kummerow <jkummerow@chromium.org>
Commit-Queue: Clemens Backes <clemensb@chromium.org>
Cr-Commit-Position: refs/heads/master@{#76344}