This reverts commit 770ace07.

Reason for revert: Breaking the V8 Arm and V8 Arm - debug builds https://ci.chromium.org/p/v8/builders/luci.v8.ci/V8%20Arm%20-%20debug/7260

Original change's description:
> [heap] Cleanup: Use std::atomic<T> instead of base::AtomicValue<T> in heap/*.
> 
> Bug: chromium:842083
> Change-Id: Idc04f9ddea326df4ac48a8c58321620660b21549
> Reviewed-on: https://chromium-review.googlesource.com/1129520
> Reviewed-by: Ulan Degenbaev <ulan@chromium.org>
> Commit-Queue: Hannes Payer <hpayer@chromium.org>
> Cr-Commit-Position: refs/heads/master@{#54389}

TBR=ulan@chromium.org,hpayer@chromium.org,mlippautz@chromium.org

Change-Id: I108bc5386ea825c2700f9b830b85a1ca8c10bf4b
No-Presubmit: true
No-Tree-Checks: true
No-Try: true
Bug: chromium:842083
Reviewed-on: https://chromium-review.googlesource.com/1134966Reviewed-by: Maya Lekova <mslekova@chromium.org>
Commit-Queue: Maya Lekova <mslekova@chromium.org>
Cr-Commit-Position: refs/heads/master@{#54398}