When a compaction space allocates a new code page, that pages needs to
be added to the Isolate::code_pages_ array used for stack unwinding.
Since the array is owned by the main thread, compaction thread cannot
directly modify it. Because of that code pages are added upon merging
of the compaction space to the main space in MergeLocalSpace.

The bug was that all code pages coming from the compaction space
were added to the code_pages_ array. However, some of the pages are
not newly allocated but merely borrowed from the main space.

This CL keeps track of all newly allocated paged by a compaction space.

Bug: v8:10900
Change-Id: Iff3ff5d608df60fb752d2e0ffc29e51f2d967936
Reviewed-on: https://chromium-review.googlesource.com/c/v8/v8/+/2418718
Commit-Queue: Ulan Degenbaev <ulan@chromium.org>
Reviewed-by: Dominik Inführ <dinfuehr@chromium.org>
Reviewed-by: Jakob Kummerow <jkummerow@chromium.org>
Cr-Commit-Position: refs/heads/master@{#70023}