%AddNamedProperty was only used by regression tests, and is easily
replaced by Object.defineProperty (or deleted, in the case of a
cctest that was designed to test it directly).

%AddElement was unused (probably due to the death of array.js).

Bug: v8:7624
Change-Id: Icc17fd7a7419aa649275414a351f176f104040e2
Reviewed-on: https://chromium-review.googlesource.com/c/1387990Reviewed-by: Yang Guo <yangguo@chromium.org>
Commit-Queue: Adam Klein <adamk@chromium.org>
Cr-Commit-Position: refs/heads/master@{#58448}