[package] ignore dunder import errors (#61148)
Summary:
Pull Request resolved: https://github.com/pytorch/pytorch/pull/61148
Changes `__import__` processing to silently skip cases where the `__import__` statement cannot be parsed. Adds failed imports to a list retrievable by `PackageExporter.failed_dunder_import_list()`.
Test Plan: Imported from OSS
Reviewed By: suo
Differential Revision: D29559680
Pulled By: Lilyjjo
fbshipit-source-id: 2513d0b9ef271c85cadc3f5a013fbd8c8de80b46
