add add_loggers implementation using PNP (#91639)
Summary:
This PR reimplements the old `add_loggers(name_a, model_a, name_b, model_b)`
API in a single-model API style, similar to PNP. This allows for memory
efficiency savings of not having to load two models.
Test plan:
```
python test/test_quantization.py -k NShadows.test_add_loggers
```
Pull Request resolved: https://github.com/pytorch/pytorch/pull/91639
Approved by: https://github.com/jerryzh168
