This reverts commit cbf028e8.

Reason for revert: Broke Mac64 GC Stress https://ci.chromium.org/p/v8/builders/ci/V8%20Mac64%20GC%20Stress/9148

Original change's description:
> [Heap] Create a fast path for young allocations.
> 
> Bug: v8:9714
> Change-Id: I3be6ea615142c8282bb67370626c7596cedf826c
> Reviewed-on: https://chromium-review.googlesource.com/c/v8/v8/+/1800304
> Reviewed-by: Ulan Degenbaev <ulan@chromium.org>
> Commit-Queue: Victor Gomes <victorgomes@google.com>
> Auto-Submit: Victor Gomes <victorgomes@google.com>
> Cr-Commit-Position: refs/heads/master@{#63729}

TBR=ulan@chromium.org,verwaest@chromium.org,victorgomes@google.com

Change-Id: I687de68a0413c62df304030deafd04661028f156
No-Presubmit: true
No-Tree-Checks: true
No-Try: true
Bug: v8:9714
Reviewed-on: https://chromium-review.googlesource.com/c/v8/v8/+/1801681Reviewed-by: Zhi An Ng <zhin@chromium.org>
Commit-Queue: Zhi An Ng <zhin@chromium.org>
Cr-Commit-Position: refs/heads/master@{#63732}