Revert of [turbofan] Combine GenericLoweringPhase and ChangeLoweringPhase. (patchset #1 id:1 of https://codereview.chromium.org/1697133002/ )

Reason for revert:
Seems to tank stuff.

Original issue's description:
> [turbofan] Combine GenericLoweringPhase and ChangeLoweringPhase.
>
> There's no need to use a dedicated ChangeLoweringPhase before we go to
> GenericLoweringPhase; instead that change lowering (which is really
> simplified lowering by now) should run together with generic lowering.
>
> R=jarin@chromium.org
>
> Committed: https://crrev.com/0835ed9caf44427755065eb45f9187678ec9844c
> Cr-Commit-Position: refs/heads/master@{#34008}

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

Review URL: https://codereview.chromium.org/1698273002

Cr-Commit-Position: refs/heads/master@{#34019}