required should be inferred from the return type of a hybrid property

With a definition like:
```
@hybrid_property
def is_active(self) -> bool:
return self.state == 'ACTIVE'
```

The resulting graphql field type is currently marked `Boolean` unless overridden by `ORMField()`. Column properties correctly determine the nullability from the column definition. It seems reasonable to do the same for the hybrid_property based on the declared type. If the return type were `bool | None`, then it would be optional, otherwise it should be required.