PPC: [es6] Re-implement rest parameters via desugaring.

PPC: [es6] Re-implement rest parameters via desugaring.

Port 510baeacbab311798d5e8795800ff773d00d062c

Original commit message:
    Kills the kRestParameter bailout/disabled optimization, and fixes
    lazily parsed arrow functions with rest parameters.

    Supercedes https://crrev.com/1235153006/

R=caitpotter88@gmail.com, joransiu@ca.ibm.com, jyan@ca.ibm.com, michael_dawson@ca.ibm.com, dstence@us.ibm.com
BUG=chromium:508074, v8:2160, v8:2700
LOG=N

Review URL: https://codereview.chromium.org/1318523006

Cr-Commit-Position: refs/heads/master@{#30574}