Revert of [turbofan] inline %StringIteratorPrototype%.next in JSBuiltinReducer. (patchset #12 id:210001 of https://codereview.chromium.org/2373983004/ )

Reason for revert:
[Sheriff] Speculative revert for win dbg: https://build.chromium.org/p/client.v8/builders/V8%20Win32%20-%20debug/builds/5029

Or we have an infra problem. Manual build before seems fine:
https://build.chromium.org/p/client.v8/builders/V8%20Win32%20-%20debug/builds/5030

Original issue's description:
> [turbofan] inline %StringIteratorPrototype%.next in JSBuiltinReducer.
>
> Implement the logic for StringIterator.prototype.next in the JSBuiltinReducer in order to allow inlining when the receiver is a JS_STRING_ITERATOR_TYPE map, built ontop of the SimplifiedOperators StringCharCodeAt and the newly added StringFromCodePoint.
>
> Also introduces a new StringFromCodePoint simplified op which may be useful for other String builtins, such as String.fromCodePoint()
>
> BUG=v8:5388
> R=bmeurer@chromium.org, mstarzinger@chromium.org
>
> Committed: https://crrev.com/aed32e0f22353527993de8bceaf246fc744558f5
> Cr-Commit-Position: refs/heads/master@{#39994}

TBR=bmeurer@chromium.org,mvstanton@chromium.org,caitp@igalia.com
# Skipping CQ checks because original CL landed less than 1 days ago.
NOPRESUBMIT=true
NOTREECHECKS=true
NOTRY=true
BUG=v8:5388

Review-Url: https://codereview.chromium.org/2397753003
Cr-Commit-Position: refs/heads/master@{#39995}