[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`

Unrelated, to bypass CI failures due to the gcc9 dependency update in Ubuntu-18.04:
- Add hack to squash older libstdc++ from conda environment in favor one from OS to `.ci/docker/install_conda.sh`
- Update bazel cuda builds to focal, as with libstdc++-6.0.32 bazel builds loose the ability to catch exceptions (probably because they link with cupti statically, but I could not found where it is done)
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/code_coverage/package/tool/summarize_jsons.py

@@ -45,7 +45,7 @@ def transform_file_name(
                 return file_path[file_path.find(folder) :]
     # remove pytorch base folder path
     if platform == TestPlatform.OSS:
-        from package.oss.utils import get_pytorch_folder
+        from package.oss.utils import get_pytorch_folder  # type: ignore[import]
 
         pytorch_foler = get_pytorch_folder()
         assert file_path.startswith(pytorch_foler)