The atomics.wait implementations need to reset the "thread in wasm" flag
during their execution, as they might handle interrupts, at which point
we assume (and occasionally check) that the "thread in wasm" flag is not
set.
Also for security it's better to reset the flag as soon as we leave wasm
code.

R=ahaas@chromium.org

Bug: chromium:1054507
Change-Id: Iad03a54819d271968568505445890fde732e6844
Reviewed-on: https://chromium-review.googlesource.com/c/v8/v8/+/2066967Reviewed-by: Andreas Haas <ahaas@chromium.org>
Commit-Queue: Clemens Backes <clemensb@chromium.org>
Cr-Commit-Position: refs/heads/master@{#66385}