Added a type field to elements to distinguish anyref, funcref and
nullref elements and do a proper type checking at compile time as
the spec requires.

R=ahaas@chromium.org

Change-Id: I31be7aa1170439859ca7ec5e20aabb2720c290b3
Reviewed-on: https://chromium-review.googlesource.com/c/v8/v8/+/2069330
Commit-Queue: Emanuel Ziegler <ecmziegler@chromium.org>
Reviewed-by: Andreas Haas <ahaas@chromium.org>
Cr-Commit-Position: refs/heads/master@{#66448}