feat: support boolean shorthand for 'cast_spaces' and add tests

[artengin]

Refs: #397

[artengin]

I’ve investigated this issue and submitted a fix.
The problem was that cast_spaces: false wasn’t being normalized into the explicit configuration expected by PHP-CS-Fixer (['space' => 'none']). Because of that, disabling the rule had no effect.

Now the shorthand form is properly resolved, and setting "cast_spaces": false in pint.json will correctly translate into the none option of PHP-CS-Fixer.

I hope my contribution will be useful, thank you! 🙏