Revert of [turbofan] Add support for copy-on-write element stores. (patchset #2 id:20001 of https://codereview.chromium.org/2218703003/ )

Reason for revert:
Breaks tree?

Original issue's description:
> [turbofan] Add support for copy-on-write element stores.
>
> This extends JSNativeContextSpecialization with support for stores to
> fast object/smi element backing stores that are marked as copy-on-write.
> In this case we first call the CopyFixedArray builtin to take a copy of
> the elements backing store, and then store the new elements back to the
> object, and finally perform the actual element store.
>
> R=epertoso@chromium.org
> BUG=v8:4470
>
> Committed: https://crrev.com/ac98ad22f049a59c48387f1bab1590f135d219c6
> Cr-Commit-Position: refs/heads/master@{#38370}

TBR=epertoso@chromium.org
# Skipping CQ checks because original CL landed less than 1 days ago.
NOPRESUBMIT=true
NOTREECHECKS=true
NOTRY=true
BUG=v8:4470

Review-Url: https://codereview.chromium.org/2220513002
Cr-Commit-Position: refs/heads/master@{#38376}