switch to getattr() for annotations

[fclivaz42]

Fixes a crash in newer python/blender versions while being retro-compatible.
Fixes the bug causing

Python: Traceback (most recent call last):
File "..../io_scene_ueformat/op/import_helpers.py", line 27, in execute
options = self.options_class.from_settings(context.scene.uf_settings)
File "..../io_scene_ueformat/options.py", line 21, in from_settings
k: v for k, v in settings.get_props().items()
~~~~~~~~~~~~~~~~~~^^
File "..../io_scene_ueformat/op/settings.py", line 23, in get_props
for key in self.__annotations__.keys():
^^^^^^^^^^^^^^^^^^^^
AttributeError: 'UFSettings' object has no attribute '__annotations__'. Did you mean: '__annotate_func__'?