(At least) Non-interactive commands should write errors to STDERR

[InvisibleSmiley]

Right now commands like migrate write errors to STDOUT. This is wrong. Errors, especially from commands that are commonly used non-interactively, need to be written to STDERR so that scripts executing Phinx can easily distinguish between information (STDOUT) and errors (STDERR), possibly redirecting either of them to different locations.

Here's how:
https://symfony.com/doc/current/console/style.html#writing-to-the-error-output