Also:
* added PHP 8.2 stubs
* refined types to make impossible scenarios more clear (like `ReflectionIntersectionType#allowsNull()`)
This is a first attempt at refining these types: the structure of these stubs is quite confusing to me,
so I don't know if this approach is correct, and if the stubs are merged together, or if entire symbols
need to be completely re-declared for each PHP version.