ParameterHandler

• Add support for symfony/yaml 8
• Fix PHP 8.5 deprecations

• Drop support for old PHP versions. The min version is now PGP 7.4.
• Drop support for old Symfony versions. The min version is now Symfony 5.4
• Mark symfony/yaml 7 as supported

Add support for Symfony 6

• Marked symfony/yaml 4 as supported to be compatible with Symfony 4

• Mark symfony/yaml 3 as supported to be compatible with Symfony 3
• Dropped support for symfony/yaml 2.2 and older (which are long unmaintained)
• Added testing on PHP 7