This reverts commit 26dad80f.

Reason for revert: Breaks d8, see https://ci.chromium.org/p/v8/builders/ci/V8%20Win32/22272

Original change's description:
> [d8] Cleanup message queues
> 
> Simplifies some of the logic of message queues in d8 and makes sure
> to delete any in-flight messages upon worker termination. Drive-by
> cleanups of some other small d8 vestiges.
> 
> R=​clemensh@chromium.org
> BUG=v8:9524
> 
> Change-Id: I587c0cb3eeed88107e7dba552389057f07c15c43
> Reviewed-on: https://chromium-review.googlesource.com/c/v8/v8/+/1710673
> Commit-Queue: Ben Titzer <titzer@chromium.org>
> Reviewed-by: Clemens Hammacher <clemensh@chromium.org>
> Cr-Commit-Position: refs/heads/master@{#62873}

TBR=titzer@chromium.org,clemensh@chromium.org

Change-Id: Ibc15d9fb76698a2bad51e3842392634fb2f0246b
No-Presubmit: true
No-Tree-Checks: true
No-Try: true
Bug: v8:9524
Reviewed-on: https://chromium-review.googlesource.com/c/v8/v8/+/1714877Reviewed-by: Maya Lekova <mslekova@chromium.org>
Commit-Queue: Maya Lekova <mslekova@chromium.org>
Cr-Commit-Position: refs/heads/master@{#62875}