ns for fx: bug fix for shadowing fp16 emulation patterns (#56384)
Summary:
Pull Request resolved: https://github.com/pytorch/pytorch/pull/56384
Enables shadow copies of fp16 emulation patterns where weights
are cast to fp16 before being passed to linear. This previously
did not work because copying of `call_method` nodes was not implemented.
Test Plan:
```
python test/test_quantization.py TestFXNumericSuiteCoreAPIs.test_linear_fp16_vs_linear_fp16_shadow_activations
```
Imported from OSS
Reviewed By: jerryzh168
Differential Revision: D27857735
fbshipit-source-id: 7c1a067f035acf7322175f8535876d0ead88a86a
