Revert of [turbofan] Run everything after representation selection concurrently. (patchset #2 id:20001 of https://codereview.chromium.org/1926023002/ )

Reason for revert:
[Sheriff] Flaky crashed here and there:
https://build.chromium.org/p/client.v8/builders/V8%20Linux/builds/9867
https://build.chromium.org/p/client.v8/builders/V8%20Linux64/builds/9589
https://build.chromium.org/p/client.v8/builders/V8%20Mac/builds/7679

Original issue's description:
> [turbofan] Run everything after representation selection concurrently.
>
> Further refactor the pipeline to even run the first scheduler (part of
> the effect control linearization) concurrently. This temporarily
> disables most of the write barrier elimination, but we will get back to
> that later.

TBR=mstarzinger@chromium.org,bmeurer@chromium.org
# Skipping CQ checks because original CL landed less than 1 days ago.
NOPRESUBMIT=true
NOTREECHECKS=true
NOTRY=true

Review-Url: https://codereview.chromium.org/1925073002
Cr-Commit-Position: refs/heads/master@{#35863}