Instead of annotating those racy reads / writes to be ignore by TSan,
just use relaxed atomics. This makes us not rely on undefined behaviour,
and is unlikely to introduce noticeable overhead.

This removes the only uses of TSAN_ANNOTATE_IGNORE_WRITES_BEGIN and
friends, which allows us to remove the whole tsan.h header.

R=ulan@chromium.org
CC=​mlippautz@chromium.org

Bug: v8:11704
Change-Id: Ie6694c0ae5b40856b56fb97253ce626ec1f4c263
Cq-Include-Trybots: luci.v8.try:v8_linux64_tsan_rel_ng
Cq-Include-Trybots: luci.v8.try:v8_linux64_tsan_isolates_rel_ng
Reviewed-on: https://chromium-review.googlesource.com/c/v8/v8/+/2859957Reviewed-by: Ulan Degenbaev <ulan@chromium.org>
Commit-Queue: Clemens Backes <clemensb@chromium.org>
Cr-Commit-Position: refs/heads/master@{#74321}