instancenorm: static quant graph mode support (#39096)
Summary:
Pull Request resolved: https://github.com/pytorch/pytorch/pull/39096
Hooks up instancenorm for graph mode static quant
Test Plan:
```
python test/test_quantization.py TestQuantizeScriptPTSQOps.test_instance_norm
```
Imported from OSS
Differential Revision: D21885258
fbshipit-source-id: 650cc5b162dda044866176fea6c345082d9788ed
