RFC: Consolidate reporting, print remaining tests

This is an RFC, I'm happy to chop it up for actual committing, but I wanted to have this to start a conversation.

This does a few things:

1) Consolidate console action during a jest run into one place. This is mostly a straight-forward move of code from bin/jest to defaultTestResultHandler.
2) Expose aggregatedResults to every callback, rather than just the end.
3) Add testsPassed as a metric in aggregatedResults so we can make sense of it before the whole run has finished.
4) Print a trailing "Waiting on..." at the bottom of the feedback.