This adds a stress test for the I64 variants of the
AtomicCompareExchange opcodes.

Bug: v8:6532
Change-Id: Iaba4f31f944a71393e5c3222d364d214ff482b9e
Reviewed-on: https://chromium-review.googlesource.com/1235913
Commit-Queue: Stephan Herhut <herhut@chromium.org>
Reviewed-by: Andreas Haas <ahaas@chromium.org>
Cr-Commit-Position: refs/heads/master@{#56261}