Use php-cs-fixer for formatting

[shish]

phpcs fixes a few things, but leaves other things inconsistent; php-cs-fixer is preferred by at least two maintainers

Making this a task instead of just doing it because php-cs-fixer doesn't officially support php 8.4 yet, and installing the current release conflicts with phpunit 12 D: But hopefully both of those things should be resolved soon

[kubawerlos]

The conflict with PHPUnit is already resolved.

PHP CS Fixer still does not officially support PHP 8.4, but you can run it without a problem using env var PHP_CS_FIXER_IGNORE_ENV=1.

Not supporting in practice means that PHP 8.4 features like property hooks or asymmetric visibility are not covered by tests yet, but that's not a problem as Safe supports PHP ^8.1, so they won't be used for a while anyway.