ns for fx: fix bug for user function in weight extraction (#62333)
Summary:
Pull Request resolved: https://github.com/pytorch/pytorch/pull/62333
We incorrectly ignored any custom relationships the user specified
in the `extract_weights` API. Fixing this and adding a test case.
Test Plan:
```
python test/test_quantization.py TestFXNumericSuiteCoreAPIs.test_user_defined_function
```
Imported from OSS
Reviewed By: hx89
Differential Revision: D29963502
fbshipit-source-id: 33ce3d4df1acb6298b6c7dcb6674015c8d14bdf4
