[quant][docs] Additonal fixes for quantize_fx docs (#84587)
Summary:
Some more clarifications for the arguments, including linking to object docs (QConfigMapping, BackendConfig) and adding types
in the doc
Test Plan:
```
cd docs
make html
```
and
visual inspection for the generated docs
Reviewers:
Subscribers:
Tasks:
Tags:
Pull Request resolved: https://github.com/pytorch/pytorch/pull/84587
Approved by: https://github.com/vkuzo
