[quant] Run weight_post_process for QAT (#33852)
Summary:
Pull Request resolved: https://github.com/pytorch/pytorch/pull/33852
This fixes an issue for QAT models. During eval if we call `prepare_qat` and `convert` before calling `load_state_dict` it throws an error because the weight info (num channels) is not updated in the observer module.
It is not an issue for per-tensor case
Fixes issue #33830
Test Plan:
python test/test_quantization.py EagerModePostTrainingQuantTest.test_eval_after_train
python test/test_quantization.py EagerModeQuantizationAwareTrainingTest.test_eval_after_train
Imported from OSS
Differential Revision: D20212996
fbshipit-source-id: a04af8fe4df2e555270ae4d6693f5777d86f8a46
