Also fix type-check to check receiver for JSReceiver, not JSObject,
and add a test for DateTimeFormat verifying that it already
has the proper behavior.

Bug: chromium:881023
Cq-Include-Trybots: luci.v8.try:v8_linux_noi18n_rel_ng
Change-Id: I950c86094dfb9634e0b7e49bcbbb022fa81a71f7
Reviewed-on: https://chromium-review.googlesource.com/1225612
Commit-Queue: Adam Klein <adamk@chromium.org>
Reviewed-by: Sathya Gunasekaran <gsathya@chromium.org>
Cr-Commit-Position: refs/heads/master@{#55880}