Port d0ccddd0

Original commit message:
       First version of the new generators implementation.

       Behind --ignition-generators. Does not yet support Turbofan.

R=neis@chromium.org, joransiu@ca.ibm.com, mbrandy@us.ibm.com, michael_dawson@ca.ibm.com, bjaideep@ca.ibm.com
BUG=

Review URL: https://codereview.chromium.org/1899283002

Cr-Commit-Position: refs/heads/master@{#35636}