NewSpace is renamed to SemiSpaceNewSpace and NewSpaceBase is renamed to
NewSpace (the new PagedSpace new space implementation will be named
PagedNewSpace).

Most usecases are updated to use the base class rather than the concrete
semi space based implementation. To that end, the base class is extended
with additional virtual methods (for delegating to the concrete class).

This CL follows these guidelines:
(*) If at a method callsite we should know the exact new space
implementation we use, we cast to the concrete class. This is the case
for example for callsites in scavenger.*.
(*) If a method is called from outside the heap implementation or should
be present regardless of the concrete implementation, that method is
made virtual.
(*) Other cases are usually methods that are specific to a concrete
implementation but the concrete implementation is not known at the
callsite and there's no clear way to nicely abstract the method. In such
cases we cast to the concrete SemiSpaceNewSpace implementation for now
and we will revisit these cases once PagedNewSpace exists.

Bug: v8:12612
Change-Id: I7b85626774ce0d785b0257bf8d32b9f50eeaf292
Reviewed-on: https://chromium-review.googlesource.com/c/v8/v8/+/3625975
Commit-Queue: Omer Katz <omerkatz@chromium.org>
Reviewed-by: Michael Lippautz <mlippautz@chromium.org>
Cr-Commit-Position: refs/heads/main@{#80482}