Joining a queue-using process can deadlock if the child process is
about to write to the queue, but the parent process wants to join the
child. To fix this, we now drain elements from a separate thread of
the main process.

Bug: v8:13113
Change-Id: Ic279e66ab84eb89a4034ff1f2c025eb850b65013
Reviewed-on: https://chromium-review.googlesource.com/c/v8/v8/+/3891116
Commit-Queue: Michael Achenbach <machenbach@chromium.org>
Reviewed-by: Alexander Schulze <alexschulze@chromium.org>
Cr-Commit-Position: refs/heads/main@{#83177}