Symfony 6 and PHP 8.2 support

Added

• Add support for PHP 8.2
• Add support for Symfony 6

Changed

• Mark all classes as final
• Add return type hints
• Print an empty string with twig breakpoint function
• Delegate Xdebug detection to composer/xdebug-handler when available

Removed

• Drop support for PHP<7.4
• Drop support for Symfony<4.4
• Drop support for Twig<2.15.3