When the --debug-code flag is turned on, we create code now which checks
if the thread-in-wasm flag has the expected value. If not, we abort
execution.

R=clemensh@chromium.org

Bug: v8:5277, v8:8554
Change-Id: I74c4e6a60b874b48f13ded9b5cee81f602e4c9fd
Reviewed-on: https://chromium-review.googlesource.com/c/1370025Reviewed-by: Clemens Hammacher <clemensh@chromium.org>
Commit-Queue: Andreas Haas <ahaas@chromium.org>
Cr-Commit-Position: refs/heads/master@{#58127}