Simplify msftidy with File.find and add fixed()

Open the door to fixing files that have things that could be fixed programmatically.

Actually using this functionality might make msftidy.rb a little bit destructive, so before I go much farther, we'll need some rspec testing on this intensely useful command line application.

That said, this PR doesn't implement anything that uses `fixed()`

[SeeRM #8497]