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: Ia7334a30b401988309e9909cfa0069da0bb6fb9f
Reviewed-on: https://chromium-review.googlesource.com/1169466Reviewed-by: Tobias Tebbi <tebbi@chromium.org>
Reviewed-by: Jakob Gruber <jgruber@chromium.org>
Commit-Queue: Tobias Tebbi <tebbi@chromium.org>
Cr-Commit-Position: refs/heads/master@{#55263}