Fix incorrect warnings in ParameterList/Dict (#48315)
Summary:
Fixes https://github.com/pytorch/pytorch/issues/46983.
The solution is based of two components:
1. The introduction of the `_initialized` attribute. This will be used during ParameterList/Dict creation methods `__init__` (introduced in https://github.com/pytorch/pytorch/issues/47772) and `__setstate__` to not trigger warnings when setting general `Module` attributes.
2. The introduction of the `not hasattr(self, key)` check to avoid triggering warnings when changing general `Module` attributes such as `.training` during the `train()` and `eval()` methods.
Tests related to the fix are added.
Pull Request resolved: https://github.com/pytorch/pytorch/pull/48315
Reviewed By: mrshenli
Differential Revision: D25130217
Pulled By: albanD
fbshipit-source-id: 79e2abf1eab616f5de74f75f370c2fe149bed4cb
