Evaluate lazy objects for partial entity loading

### Technical TODO

With PHP 8.4 lazy objects were introduced https://www.php.net/manual/en/language.oop5.lazy-objects.php
In his talk on SymfonyCon '25 @beberlei talked about using this for loading partial entities in Doctrine ORM.
https://github.com/SymfonyCon/2025-talks?tab=readme-ov-file#how-native-lazy-objects-will-change-doctrine-and-symfony-forever
The objects have the same class as fully loaded objects, but only a few properties are set.
We should evaluate if we could exchange the [PartialEntity](https://github.com/shopware/shopware/blob/v6.7.5.0/src/Core/Framework/DataAbstractionLayer/PartialEntity.php) with this or a similar approach.
This gives the advantage, that we can still typehint normal entities instead a generic quite undefined one.

Start by reading src/Core/Framework/DataAbstractionLayer/PartialEntity.php and the PHP 8.4 lazy objects documentation, then review the linked SymfonyCon talk for the proposed partial-entity approach. Done means producing an evaluation of whether PartialEntity can be replaced by lazy objects or a similar approach while retaining normal entity type hints.

Written by the indexing model from the issue text.