[pkg] Improve mocked module detection by combining mocked object errors with the rest of the errors in PackageExporter (#74315)
Summary:
Pull Request resolved: https://github.com/pytorch/pytorch/pull/74315
Now instead of spitting out a NotImplemented Error when the Package Exporter finds an object for a mocked module, it combines these errors with the rest of the Packaging Errors of PackageExporter to get something like
```
torch.package.package_exporter.PackagingError:
* Module was mocked out, but is still being used in the package.Please intern or extern the mocked modules if objects are supposed to be inthe package.
package_a
Context: Object(s) '['PackageASubpackageObject']' from module package_a was mocked out during packaging but is being used in resource - obj.pkl in package obj.
package_a.subpackage
Context: Object(s) '['PackageASubpackageObject']' from module package_a.subpackage was mocked out during packaging but is being used in resource - obj.pkl in package obj.
```
This makes it significantly easier to fix mocked object errors as they all should appear at once.
Test Plan: Imported from OSS
Reviewed By: aivanou
Differential Revision: D34932200
Pulled By: PaliC
fbshipit-source-id: 7f12bd88dbfbad974fd04b5dcaba3203b5c68a04
(cherry picked from commit 73df434ddd3e26f0e4c5ea3dd2ca1b6984736213)
