[Quant][fx] Add default configs for fixed qparams ops (#80184)
Summary: This commit adds qconfigs with special observers for fixed
qparams ops in get_default_qconfig_mapping and
get_default_qat_qconfig_mapping. For correctness, we also require
users to use these special observers if we detect these fixed
qparams ops in prepare.
Test Plan:
python test/test_quantization.py TestQuantizeFx
python test/test_quantization.py TestQuantizeFxOps
Reviewers: jerryzh168, vkuzo
Subscribers: jerryzh168, vkuzo
Differential Revision: [D37396379](https://our.internmc.facebook.com/intern/diff/D37396379)
Pull Request resolved: https://github.com/pytorch/pytorch/pull/80184
Approved by: https://github.com/jerryzh168
