Add Laravel 13 Support

[oliverearl]

This pull request updates the codebase to support Laravel 13 and PHP 8.5, while maintaining compatibility with previous versions. The changes ensure that the package can be tested and used with the latest versions of Laravel and PHP, as well as their associated testing tools.

Misc:
I also had to refactor a method to make Phpstan happy. This has no functional difference; just a slightly different approach.

Framework and PHP version support:

• Updated the composer.json requirements to allow both Laravel 13 and Laravel 12 (illuminate/contracts: ^13.0|^12.0) and both Testbench 11 and 10 (orchestra/testbench: ^11.0.0|^10.1.0).
• Updated the PHP version requirement in the PHPStan workflow to use PHP 8.5.

CI and testing matrix updates:

• Extended the GitHub Actions test matrix to include Laravel 13 and Testbench 11, in addition to existing support for Laravel 12 and Testbench 10.