This also introduces two new simplified operators, ObjectIsSafeInteger
and NumberIsSafeInteger.

Bug: v8:7340, v8:7250
Change-Id: I9a3028d844e6614ed248a03fe24b431fb54938f0
Reviewed-on: https://chromium-review.googlesource.com/973221Reviewed-by: Benedikt Meurer <bmeurer@chromium.org>
Commit-Queue: Sigurd Schneider <sigurds@chromium.org>
Cr-Commit-Position: refs/heads/master@{#52112}