NewSpace and PagedSpace both inherit from SpaceWithLinearArena and
implement allocation logic on top of it. The parts of the allocation
path that deal specifically with the linear allocation area are
equivalent (only minor syntactic differences between them).

This CL refactors the allocation from a linear allocation area out of
NewSpace and PagedSpace and moves it to SpaceWithLinearArea. This
eliminates code duplication and keeps everything generally still working
the same.

This is done as part of an effort to create a stable NewSpace interface
to allow introducing an alternative paged new space.

Bug: v8:12612
Change-Id: Ie24345a2d51f6e67ebe8a1d67e586038f7aec8de
Reviewed-on: https://chromium-review.googlesource.com/c/v8/v8/+/3578547Reviewed-by: Dominik Inführ <dinfuehr@chromium.org>
Reviewed-by: Michael Lippautz <mlippautz@chromium.org>
Commit-Queue: Omer Katz <omerkatz@chromium.org>
Cr-Commit-Position: refs/heads/main@{#79955}