Update PHPUnit to 11.0 and PHPCS to 4.0

Update PHPUnit to 11.0 and PHPCS to 4.0 - Update require-dev dependencies: PHPUnit to ^11.0 and PHPCS to ^4.0. - Update CI workflows to test on PHP 8.2, 8.3, 8.4, and 8.5. - Refactor tests to use PHPUnit 11 attributes instead of annotations. - Update README.md to reflect supported PHP versions for testing. - Remove DateConverterTest.php (unused stub). - Update phpunit.xml.dist to PHPUnit 11 format. - Add .phpunit.cache to .gitignore. - Enable PCOV for coverage in CI. Co-authored-by: hussainweb <1040271+hussainweb@users.noreply.github.com>