Switch phpstan to include phpstan.neon.dist

[deviantintegral]

As I noted at https://github.com/Lullabot/drainpipe/pull/216, phpstan generally recommends and expects a .dist file to be committed to the repo, and phpstan.neon to be git ignored. As well, PHPStorm throws an error that phpstan.neon.dist doesn't exist.

Instead, lets:

1. Copy the configuration as phpstan.neon.dist via composer scaffold.
2. Get rid of -c in our task:static tests.