In the process, use the correct ArrayPrototype* naming convention for
the slice and splice builtins.

Change-Id: I1f85e5512dbde8f92e7c764aef9f137d0a6693e0
Reviewed-on: https://chromium-review.googlesource.com/c/1350869Reviewed-by: Michael Stanton <mvstanton@chromium.org>
Commit-Queue: Daniel Clifford <danno@chromium.org>
Cr-Commit-Position: refs/heads/master@{#57840}