Before, splice was implemented with a C++ fast path and a
comprehensive JavaScript version.

This impl. is entirely in Torque with a fastpath for SMI,
DOUBLE and OBJECT arrays, and a comprehensive slow path.
The same level of "sparse" array support as given by the
array.js implementation is included.

Cq-Include-Trybots: luci.v8.try:v8_linux_noi18n_rel_ng
Change-Id: Ibfa3407ed75b9ad15ac54cce446b3952e38f90a9
Reviewed-on: https://chromium-review.googlesource.com/1039190Reviewed-by: Yang Guo <yangguo@chromium.org>
Reviewed-by: Tobias Tebbi <tebbi@chromium.org>
Commit-Queue: Michael Stanton <mvstanton@chromium.org>
Cr-Commit-Position: refs/heads/master@{#54974}