instancenorm: eager mode QAT support (#39093)
Summary:
Pull Request resolved: https://github.com/pytorch/pytorch/pull/39093
Adds eager mode QAT support for instancenorm
Test Plan:
```
python test/test_quantization.py TestQuantizationAwareTraining.test_normalization
```
Imported from OSS
Differential Revision: D21885264
fbshipit-source-id: 7753995eed895bad26f713a857c6b0d194ea99d9
