[quant][fx] Support producing reference quantized patterns for dynamic quantization (#89248)
Summary:
split the is_decomposed logic for `_replace_observer_with_quantize_dequantize_node` in a separate function and added support for dynamic quantization in the decomposed version of this function.
In case of dynamic quantization, we'll produce the following reference quantized pattern in decomposed mode:
```
x -> choose_qparams -> quantize_per_tensor -> dequantize_per_tensor -> linear
```
Test Plan:
python test/test_quantization.py -k test__convert_to_reference_decomposed_fx_dynamic_quant
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Subscribers:
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Pull Request resolved: https://github.com/pytorch/pytorch/pull/89248
Approved by: https://github.com/vkuzo
