ns for fx: additional bugfix for user defined functions (#56762)
Summary:
Pull Request resolved: https://github.com/pytorch/pytorch/pull/56762
Adds a test case for wrapped sigmoid, and fixes the following issues
to make it pass in NS:
* allows comparing between x.sigmoid() and torch.sigmoid(x), if they are related
* allows dtype cast from FP32_OR_INT8 to FP32, via dequantize (this will be improved later)
Test Plan:
```
python test/test_quantization.py TestFXNumericSuiteCoreAPIs.test_user_defined_function
```
Imported from OSS
Reviewed By: jerryzh168
Differential Revision: D27960766
fbshipit-source-id: 02935d2f400aa0b8f3d51bbf664a6c8ca89aa811
