This CL also introduces an effect dependent simplified operator
DateNow and associated lowerings.

Bug: v8:7340, v8:7250
Change-Id: Icd4a8c3c45a8dbe7ef490fc3ee68c0c68bbed011
Reviewed-on: https://chromium-review.googlesource.com/1024836
Commit-Queue: Sigurd Schneider <sigurds@chromium.org>
Reviewed-by: Benedikt Meurer <bmeurer@chromium.org>
Cr-Commit-Position: refs/heads/master@{#52782}