get_function_name_from_frame() has bugs

It's possible to get two functions in the same file with the same name. For example
```py
class CameraNotifier(NSObject):
def init(self):
def register(events, center):
```
causes a function named "CameraNotifier.register" to be recorded, which may conflict with an actual method of the same class with the same name.

(Note that usually this is resolved in `pyannotate` by looking at the line numbers.)