This new FreeList should be a reasonable replacement for our old
FreeListLegacy: it is slightly less efficient (~1%), but uses much
less memory (often 5% less old_space size).

It is based on FreeListMany, with the following additions:

  - A cache to waste less time iterating empty categories

  - A fast path for allocations done in the runtime and generated code

  - A slow path (the same as FreeListMany actually) for allocations
    done in the GC.

Bug: v8:9329
Change-Id: Ifc10b88df7861266a721afd2c6e6d8357255ec4e
Reviewed-on: https://chromium-review.googlesource.com/c/v8/v8/+/1762292
Commit-Queue: Darius Mercadier <dmercadier@google.com>
Reviewed-by: Ulan Degenbaev <ulan@chromium.org>
Cr-Commit-Position: refs/heads/master@{#63345}