If the gc foreground task is running, we don't expect any wasm code to
be live on the stack.
This CL adds a SLOW_DCHECK for this assumption.

R=mstarzinger@chromium.org

Bug: v8:8217
Change-Id: I0c221f6acaebd8c622d0f55ff85f69105482942f
Reviewed-on: https://chromium-review.googlesource.com/c/v8/v8/+/1609541Reviewed-by: Michael Starzinger <mstarzinger@chromium.org>
Commit-Queue: Clemens Hammacher <clemensh@chromium.org>
Cr-Commit-Position: refs/heads/master@{#61449}