[Reland] Update mypy to 1.4.1 (#105227)

This PR re-lands
- [Typing] Fix PEP 484 Violation (#105022)
- Update mypy to 1.4.1 (#91983)

That were reverted due to the conflict with internal source repo.

Mostly fixes for PEP-484 violation (i.e. when default arg is set to None, but type is not annotated as optional)
Plus few real fixes:
  - Add missing `_get_upgraders_entry_map` to `torch/_C/__init__.pyi`
  - Add missing return statement to `torch._export. deserialize_graph`
  - Fix error message in `torch.ao.ns.fx.weight_utils.get_lstm_mod_weights`
  - Add assert it `torch/optim/optimizer.py` that Optional list is not None
TODO (in followup PR):
  - Fix erroneous `isinstance` check in `torch/ao/quantization/_pt2e/qat_utils.py`
Pull Request resolved: https://github.com/pytorch/pytorch/pull/105227
Approved by: https://github.com/atalman, https://github.com/albanD, https://github.com/Skylion007

tools/setup_helpers/generate_code.py

@@ -10,7 +10,7 @@ try:
     # use faster C loader if available
     from yaml import CSafeLoader as YamlLoader
 except ImportError:
-    from yaml import SafeLoader as YamlLoader  # type: ignore[misc]
+    from yaml import SafeLoader as YamlLoader  # type: ignore[assignment, misc]
 
 NATIVE_FUNCTIONS_PATH = "aten/src/ATen/native/native_functions.yaml"
 TAGS_PATH = "aten/src/ATen/native/tags.yaml"