This fixes a deadlock that was detected by layout tests executing with
--future (hence enabling wasm code gc). It did not fail anywhere in v8
because GC is only triggered once we have > 1MB potentially dead code.
I plan to add a '--stress-wasm-code-gc' flag, which lowers this limit
to zero, thereby triggering GC when finding a single potentially dead
code. This mode found this issue, but also finds more, so I need to fix
other issues before enabling these stress tests.

R=mstarzinger@chromium.org

Bug: v8:8217
Change-Id: I373955b90c8b79d7b9e16184729f45db947eeeab
Reviewed-on: https://chromium-review.googlesource.com/c/v8/v8/+/1583728Reviewed-by: Michael Starzinger <mstarzinger@chromium.org>
Commit-Queue: Clemens Hammacher <clemensh@chromium.org>
Cr-Commit-Position: refs/heads/master@{#61034}