[quant] Implement unsqueeze/squeeze for per-channel qtensor (#38247)
Summary:
Pull Request resolved: https://github.com/pytorch/pytorch/pull/38247
Per-channel quantized tensor axis value is shifted based on the unsqueeze/squeeze dim
Test Plan:
python test/test_quantization.py TestQuantizedTensor.test_qtensor_unsqueze
Imported from OSS
Differential Revision: D21550293
fbshipit-source-id: 90ea4a1bd637588360b3228cb5af9176176eb033
