Script to regen test fixture

I really super extra hate this test suite. It's fine for adding a few tests, but when you need to update the AST for tens of tests it really sucks. This script runs all the tests and pretty prints their results back into the test fixture.

There are some downsides to this script:
1) Damages git blame
2) Nukes comments (luckily there's only one)

There are some upsides to this script:
1) Makes me not want to kill myself
2) Demonstrates how this test suite is a pain to work with.
3) Enables changes that were unthinkable before due to the pain of updating the tests, like fixing some property from undefined to null.

I've included the results of this script. I think this script might be useful to other people. I can always not check in the output of the script, and instead try and just merge the updated tests that I care about.
necessary? Would prefer to leave upstream stuff like this as-is (unless there's a really good reason?)