quant doc: improve rendered documentation for backend_config_dict
Summary:
This improves the documentation page for backend_config_dict to render
the configurations in a human readable format, such as
```
{
'pattern': torch.nn.modules.pooling.AdaptiveAvgPool1d,
'dtype_configs': [
{
'input_dtype': torch.quint8,
'output_dtype': torch.quint8,
},
{
'input_dtype': torch.float16,
'weight_dtype': torch.float16,
'bias_dtype': torch.float16,
'output_dtype': torch.float16,
},
],
'observation_type': ObservationType.OUTPUT_SHARE_OBSERVER_WITH_INPUT,
},
```
The results are also now sorted alphabetically by the normalized name of
the root op in the pattern.
A couple of utility functions are created to help with this. If in the future
we convert backend_config_dict to use typed objects, we can move this logic
to the objects at that time.
Test plan:
```
cd docs
make html
cd build
python -m server.http
// renders correctly, example: https://gist.github.com/vkuzo/76adfc7c89e119c59813a733fa2cd56f
```
Pull Request resolved: https://github.com/pytorch/pytorch/pull/77535
Approved by: https://github.com/andrewor14
