dbr quant: support for custom leaf modules, part 2/x (#70335)
Summary:
Pull Request resolved: https://github.com/pytorch/pytorch/pull/70335
Adds test case that functions are not quantized inside custom leaf modules.
No logic change needed as it already works correctly.
Note: FX scripting rewriter does not go into modules without auto-quant,
which is why we are using torch.jit.trace to look at the graph.
Test Plan:
```
python test/test_quantization.py TestQuantizeDBR.test_prepare_custom_config_dict_non_traceable_module_class
```
Reviewed By: jerryzh168
Differential Revision: D33286370
Pulled By: vkuzo
fbshipit-source-id: 26c81c9e1ce7c4d38ddc1e318730cf1eaa25ff69
