Merge changes Ia3853e46,Ic32af2ec,I79c6cc12,Idfd59472,I68720661

* changes:
  Refine OatStatus enum.
  Factor out code for picking the best oat file.
  Move dumping of oat file status inside of the OatFileAssistant.
  Remove OatFileAssistant IsOutOfDate, IsUpToDate, and NeedsRelocation.
  Simplify decision of which is the best oat file.