ns for fx: additional bugfix for user defined functions (#57028)
Summary:
Pull Request resolved: https://github.com/pytorch/pytorch/pull/57028
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
```
Reviewed By: jerryzh168
Differential Revision: D28030089
Pulled By: vkuzo
fbshipit-source-id: b237353e2d564a4476f409df461746a259015a4b
