ns for fx: allow comparing int8 to int8 for functionals (#56742)
Summary:
Pull Request resolved: https://github.com/pytorch/pytorch/pull/56742
Fixes a bug to allow shadowing of linear and conv functionals.
The bug is to only detach tensors, not all objects.
Test Plan:
```
python test/test_quantization.py TestFXNumericSuiteCoreAPIs.test_int8_shadows_int8_fun
```
Imported from OSS
Reviewed By: jerryzh168
Differential Revision: D27960767
fbshipit-source-id: abc911ca4b9edafd1effb9dada7731981538c2df
