This CL changes Array#sort to use the generic path for fast elements
kinds if --force-slow-path is present. Note that the IsFastJSArray macro
includes this check but not the Cast itself.

R=jgruber@chromium.org

Bug: v8:8215
Change-Id: I1135ab9db15effd86020f49f4ae23ba1e1da07f8
Reviewed-on: https://chromium-review.googlesource.com/c/1435940Reviewed-by: Jakob Gruber <jgruber@chromium.org>
Commit-Queue: Simon Zünd <szuend@chromium.org>
Cr-Commit-Position: refs/heads/master@{#59097}