This reverts commit 3ff4b447.

Reason for revert: Does not handle V8_INTL_SUPPORT correctly

Original change's description:
> [turbofan] Move String.* functions to JSCallReducer
> 
> Bug: v8:7250, v8:7340
> Change-Id: Ibb8d5badf89c66bd9bcb6bb390256ae81d0e899c
> Reviewed-on: https://chromium-review.googlesource.com/913208
> Commit-Queue: Sigurd Schneider <sigurds@chromium.org>
> Reviewed-by: Benedikt Meurer <bmeurer@chromium.org>
> Cr-Commit-Position: refs/heads/master@{#51505}

TBR=sigurds@chromium.org,bmeurer@chromium.org

Change-Id: I6efb3b758b0fcadc012a90c4175de3c1ebccee95
No-Presubmit: true
No-Tree-Checks: true
No-Try: true
Bug: v8:7250, v8:7340
Reviewed-on: https://chromium-review.googlesource.com/934267Reviewed-by: Sigurd Schneider <sigurds@chromium.org>
Commit-Queue: Sigurd Schneider <sigurds@chromium.org>
Cr-Commit-Position: refs/heads/master@{#51507}