This reverts commit 7b7df7db.

Reason for revert: Still breaks gc-stress bots: https://ci.chromium.org/p/v8/builders/ci/V8%20Linux%20-%20gc%20stress/24466

Original change's description:
> Reland "[Heap] Create a fast path for young allocations."
> 
> Disable a flaky test.
> 
> This is a reland of cbf028e8
> 
> 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}
> 
> Bug: v8:9714
> Change-Id: Ifbd8617be1b8c58cb1552fe88c52eafd9d6e9c7d
> Reviewed-on: https://chromium-review.googlesource.com/c/v8/v8/+/1801840
> Commit-Queue: Victor Gomes <victorgomes@google.com>
> Commit-Queue: Ulan Degenbaev <ulan@chromium.org>
> Auto-Submit: Victor Gomes <victorgomes@google.com>
> Reviewed-by: Ulan Degenbaev <ulan@chromium.org>
> Cr-Commit-Position: refs/heads/master@{#63744}

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

Change-Id: Ie041a7ff25adb9edc7c44ebb259912e66dfb9da1
No-Presubmit: true
No-Tree-Checks: true
No-Try: true
Bug: v8:9714
Reviewed-on: https://chromium-review.googlesource.com/c/v8/v8/+/1801852Reviewed-by: Clemens Hammacher <clemensh@chromium.org>
Commit-Queue: Clemens Hammacher <clemensh@chromium.org>
Cr-Commit-Position: refs/heads/master@{#63747}