We'll be able to optimize rest parameters in TurboFan similarly to the arguments array. This CL restores the previous behavior, and a follow-on will enable TurboFan optimization.

(TBR for rossberg since we discussed the revert beforehand. The only changes are a few lines related to tests and rebasing.)

TBR=rossberg@chromium.org
BUG=

Review URL: https://codereview.chromium.org/1537683002

Cr-Commit-Position: refs/heads/master@{#33024}