We want to get rid of the atomicops library, hence switch all uses to
std::atomic.

R=mlippautz@chromium.org

Bug: v8:8926, v8:8834

Cq-Include-Trybots: luci.v8.try:v8_linux64_tsan_rel
Change-Id: I7966d4ea98c5dd2ff712b1d84a6877f407f55ec7
Reviewed-on: https://chromium-review.googlesource.com/c/v8/v8/+/1518176Reviewed-by: Michael Lippautz <mlippautz@chromium.org>
Commit-Queue: Clemens Hammacher <clemensh@chromium.org>
Cr-Commit-Position: refs/heads/master@{#60202}