Reflection for virtual `CodeIgniter\Entity\Entity` properties

> By default, PHPStan does not know what is the relation of `$casts` to the properties of Entities. We need to teach it that the content of `$casts` influence the type of the properties.

_Originally posted by @paulbalandan in https://github.com/CodeIgniter/phpstan-codeigniter/issues/7#issuecomment-1803636422_
            