This CL also removes the ElementsAccessor "slice" implementation, as
the runtime function is the last use site.

R=verwaest@chromium.org

Bug: v8:9183
Change-Id: If268e20120e7c7bb4a58d9560482b35896b0992f
Reviewed-on: https://chromium-review.googlesource.com/c/v8/v8/+/1617662Reviewed-by: Toon Verwaest <verwaest@chromium.org>
Reviewed-by: Yang Guo <yangguo@chromium.org>
Commit-Queue: Simon Zünd <szuend@chromium.org>
Cr-Commit-Position: refs/heads/master@{#61635}