SpaceWithLinearArea will holds a ref to a struct containing
original_top_ and original_limit_ as well the lock used to sync them
for querying IsPendingAllocation.

PagedSpace is split into PagedSpaceBase (that holds all funcitonality)
and PagedSpace. The actual fields are owned by PagedSpace and NewSpace.

This is done in preparation for PagedNewSpace to allow PagedSpaceiBase
and NewSpace to share the same original_top_ and original_limit_ fields.

Bug: v8:12612
Change-Id: Iefbbd5209c5553db4ee16cb261734e6479e0f23f
Reviewed-on: https://chromium-review.googlesource.com/c/v8/v8/+/3644795
Commit-Queue: Omer Katz <omerkatz@chromium.org>
Reviewed-by: Michael Lippautz <mlippautz@chromium.org>
Cr-Commit-Position: refs/heads/main@{#80549}