Add support for phpunit.dist.xml configuration file

[takamichi]

This PR adds support for recognizing phpunit.dist.xml, which was introduced in PHPUnit 10.

Currently, phpunit.xml and phpunit.xml.dist are supported, but phpunit.dist.xml is not. This PR adds phpunit.dist.xml as a resolution target and aligns the lookup order with PHPUnit:

1. phpunit.xml
2. phpunit.dist.xml
3. phpunit.xml.dist

• https://docs.phpunit.de/en/12.5/textui.html#configuration
• https://github.com/sebastianbergmann/phpunit/blob/10.0.0/src/TextUI/Configuration/Cli/XmlConfigurationFileFinder.php#L54-L56

[Copilot]

Pull request overview

This PR updates the Laravel adapter’s PHPUnit configuration file discovery to recognize the newer phpunit.dist.xml name (introduced in PHPUnit 10) and to match PHPUnit’s documented lookup precedence.

Changes:

• Add phpunit.dist.xml as a configuration file candidate.
• Align configuration file lookup order to: phpunit.xml → phpunit.dist.xml → phpunit.xml.dist.

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[Copilot]

This change alters configuration file resolution order and adds support for phpunit.dist.xml, but there’s no automated coverage ensuring the intended precedence (phpunit.xml > phpunit.dist.xml > phpunit.xml.dist) stays correct. Consider adding a unit/integration test that manipulates these files (e.g., in the tests/LaravelApp fixture) and asserts which config is selected when multiple candidates exist.