Now there is just one kind, corresponding to what was called "initial" before.
Replacement for "suspend": when the parser sees a yield in JS code, it
will turn it into a Yield node but wrap its argument in an iterator result
object.  Replacement for "final": the parser simply inserts a return statement
instead.

R=littledan@chromium.org, mstarzinger@chromium.org
BUG=

Review URL: https://codereview.chromium.org/1751613004

Cr-Commit-Position: refs/heads/master@{#34515}