BUGFIX: Support PHP 8+ named arguments in proxy constructors
This change enables Flow proxy classes to support PHP 8+ named argument syntax by including the original constructor parameter signature in generated proxies, fixing compatibility issues with modern PHP code and reflection-based serializers.
The proxy constructor now always includes parameters matching the original constructor signature, with all parameters made nullable and given null default values to maintain dependency injection flexibility. This allows both named and positional argument syntax while preserving backward compatibility with existing DI patterns.
Resolves #3076
Note: This PR is currently based on https://github.com/neos/flow-development-collection/pull/3494 - so merge that before this one.