Add scenario for generating proxies for intersection types in class properties/parameters/methods

[Ocramius]

Similar to #727, we need to expand our testing into intersection types.

Luckily, intersection types do not currently support nullability ( https://wiki.php.net/rfc/pure-intersection-types ), and only operate with object-alike types, which should make the integration (hopefully) straightforward.

For this, we probably need to add intersection types in new classes replicating:

• ClassWithPhp80TypedMethods
• ClassWithMixedTypedProperties
• anything arising from #727

We need to then integrate those new classes into scenarios that already verify codegen for the ones referenced above.