This reverts commit 064ee3c8.

Reason for revert: Causing blink_web_tests to fail on builder "WebKit Linux MSAN"
https://bugs.chromium.org/p/chromium/issues/detail?id=1153968

Original change's description:
> Reland "[wasm]: Use CancelAndDetach and barrier on BackgroundCompileJob."
>
> Reason for revert: Data race:
> https://ci.chromium.org/p/v8/builders/ci/V8%20Linux64%20TSAN/34121
>
> It was assume that MockPlatform runs everything on 1 thread. However,
> MockPlatform::PostJob previously would schedule the job through
> TestPlatform, which eventually posts concurrent tasks, thus causing
> data race.
> Fix: Manually calling NewDefaultJobHandle and passing the MockPlatform
> ensures the jobs also run sequentially.
>
> Additional change:
> - CancelAndDetach is now called in ~CompilationStateImpl() to make sure
> it's called in sequence with ScheduleCompileJobForNewUnits
>
> Original CL description:
> To avoid keeping around a list of job handles, CancelAndDetach() is
> used in CancelCompilation. Dependency on WasmEngine is handled by a
> barrier that waits on all jobs to finish.
>
> Reviewed-on: https://chromium-review.googlesource.com/c/v8/v8/+/2498659
> Commit-Queue: Jakob Kummerow <jkummerow@chromium.org>
> Reviewed-by: Ulan Degenbaev <ulan@chromium.org>
> Reviewed-by: Clemens Backes <clemensb@chromium.org>
> Reviewed-by: Jakob Kummerow <jkummerow@chromium.org>
> Cr-Original-Commit-Position: refs/heads/master@{#71074}
> Change-Id: Ie9556f7f96f6fb9a61ada0e5cbd58d4fb4a0f571
> Reviewed-on: https://chromium-review.googlesource.com/c/v8/v8/+/2559137
> Commit-Queue: Etienne Pierre-Doray <etiennep@chromium.org>
> Reviewed-by: Andreas Haas <ahaas@chromium.org>
> Cr-Commit-Position: refs/heads/master@{#71459}

TBR=ulan@chromium.org,jkummerow@chromium.org,ahaas@chromium.org,clemensb@chromium.org,etiennep@chromium.org
Bug: chromium:1153968, v8:11209, v8:11210, v8:11212

# Not skipping CQ checks because original CL landed > 1 day ago.

Change-Id: I2c8406bea81ee7cf6c5726c2fec50fffdce09611
Reviewed-on: https://chromium-review.googlesource.com/c/v8/v8/+/2566446Reviewed-by: Clemens Backes <clemensb@chromium.org>
Commit-Queue: Clemens Backes <clemensb@chromium.org>
Cr-Commit-Position: refs/heads/master@{#71519}