This gets rid of the Star bytecodes that were always dispatched to from
ToObject.
ToObject now outputs to register instead of to the accumulator and
ForInPrepare gets the receiver object from an input register.

BUG=v8:4820
LOG=n

Review-Url: https://codereview.chromium.org/2189463006
Cr-Commit-Position: refs/heads/master@{#38177}