This reverts commit ac0661b3.

Reason for revert: Clusterfuzz unhappy: chromium:783019 chromium:783035

Original change's description:
> Reland^5 "[turbofan] eagerly prune None types and deadness from the graph"
>
> This gives up on earlier attempts to interpret DeadValue as a signal of
> unreachable code. This does not work because free-floating dead value
> nodes, and even pure branch nodes that use them, can get scheduled so
> early that they get reachable. Instead, we now eagerly remove branches
> that use DeadValue in DeadCodeElimination and replace DeadValue inputs
> to value phi nodes with dummy values.
>
> Reland of https://chromium-review.googlesource.com/715716
>
> Bug: chromium:741225 chromium:776256
> Change-Id: I251efd507c967d4a8882ad8fd2fd96c4185781fe
> Reviewed-on: https://chromium-review.googlesource.com/727893
> Commit-Queue: Tobias Tebbi <tebbi@chromium.org>
> Reviewed-by: Jaroslav Sevcik <jarin@chromium.org>
> Cr-Commit-Position: refs/heads/master@{#49188}

TBR=jarin@chromium.org,tebbi@chromium.org

Bug: chromium:741225 chromium:776256 chromium:783019 chromium:783035
Change-Id: I6a8fa3a08ce2824a858ae01817688e63ed1f442e
Reviewed-on: https://chromium-review.googlesource.com/758770Reviewed-by: Tobias Tebbi <tebbi@chromium.org>
Commit-Queue: Tobias Tebbi <tebbi@chromium.org>
Cr-Commit-Position: refs/heads/master@{#49262}