Support __call__ on metaclasses

Currently we don't handle `__call__()` on metaclasses correctly. For example:

```python
class M(type):
    def __call__(self, x: int) -> Any: ...

class C(metaclass=M): ...

C(x=1)
```
results in a false positive. Also similarly handling of metaclass `__call__()` in protocols is not very principled, see e.g. https://github.com/python/mypy/pull/14121