This CL introduces a JSOperator for Array.isArray and moves the
corresponding lowering to JSCallReducer and JSTypedLowering.

Bug: v8:7340, v8:7250
Change-Id: Iaa7ced2ad34bec8cccc9da1041007261168cf4b3
Reviewed-on: https://chromium-review.googlesource.com/1025092
Commit-Queue: Sigurd Schneider <sigurds@chromium.org>
Reviewed-by: Benedikt Meurer <bmeurer@chromium.org>
Cr-Commit-Position: refs/heads/master@{#52757}