[quant][refactor tests] Split test_quantize into test_quantize_eager_ptq, test_quantize_eager_qat and test_fusion (#58927)
Summary:
Pull Request resolved: https://github.com/pytorch/pytorch/pull/58927
Part of larger re-factor of quantization tests to make it clearer as to which test belongs where.
proposed folder structure
```
test/quantization
- bc/
- test_backward_compatibility.py
- core/
- test_quantized_kernels.py
- test_quantized_workflow_ops.py
- test_quantized_tensor.py
- test_workflow_module.py
- eager/
- test_quantize_eager_ptq.py
- test_quantize_eager_qat.py
- test_fusion.py
- equalization/
- test_equalize_eager.py
- test_bias_correction_eager.py
- fx/
- test_quantize_fx.py
- jit/
- test_quantize_jit.py
- test_fusion_passes.py
- numeric_suite/
- test_numeric_suite_fx.py
- test_numeric_suite_eager.py
```
Test Plan:
python test/test_quantization.py
Imported from OSS
Reviewed By: raghuramank100
Differential Revision: D28683926
fbshipit-source-id: f84a4271c77c418ce9751196241933ea8cc14913
