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: I9b7cca83703775b1ddee4f16f51b7ad6535bb67c
Reviewed-on: https://chromium-review.googlesource.com/c/v8/v8/+/1520717Reviewed-by: Michael Lippautz <mlippautz@chromium.org>
Commit-Queue: Clemens Hammacher <clemensh@chromium.org>
Cr-Commit-Position: refs/heads/master@{#60233}