ns for fx: enable user defined functions for graph matching (#56283)
Summary:
Pull Request resolved: https://github.com/pytorch/pytorch/pull/56283
Exposes the `base_name_to_sets_of_related_ops` variable
to the graph matching API, so that users can add relationships
for custom functions. This is needed to enable full support of
external functions for custom backends.
The next PR will extend this to the NS APIs.
Test Plan:
```
python test/test_quantization.py TestFXGraphMatcher.test_user_defined_function
```
Imported from OSS
Reviewed By: jerryzh168
Differential Revision: D27830410
fbshipit-source-id: 8688cf697d388c52e3d18f108765edfca3c3d3aa
