Add support for ReflectionClass::newLazyGhost of PHP 8.4

[beberlei]

Our goal is that we can completely replace all kinds of code for proxy generation and proxy usage with the new lazy objects feature of PHP 8.4: https://wiki.php.net/rfc/lazy-objects

In 3.x we can add support for optionally using lazy objects, and in 4.x we increase the requirement for PHP to 8.4 and automatically always use lazy objects.

The benefit of lazy objects is that we don't need code-generation anymore, and that it also allows us to treat partial objects as lazy objects that can load their missing properites only when accessed.

Todos

• Due to property hooks and lazy initialization interactions, this PR also needs to make sure we replace all ReflectionProperty::getValue calls with ReflectionProperty::getRawValue and ReflectionProperty::setValue with ReflectionProperty::setValueWithoutLazyInitialization.
• Move from ClassMetadata::$reflFields to a new abstraction PropertyAccessor that avoids us having to extend ReflectionProperty for our edge cases (enums, typed no default, embedded, ....).

Future

As a next step this also allows us to implement a feature to mark properties as lazy, meaning that they are never fully fetched on the first query unless specify in the query (query hint? dql keyword?).