instancenorm: eager static quant support (#39091)
Summary:
Pull Request resolved: https://github.com/pytorch/pytorch/pull/39091
Adds eager mode static quant support for instancenorm.
Test Plan:
```
python test/test_quantization.py TestPostTrainingStatic.test_normalization
python test/test_quantization.py TestStaticQuantizedModule.test_instance_norm
```
Imported from OSS
Differential Revision: D21885265
fbshipit-source-id: 277506faf108f3561867cd8449a2390b7a44c462
