[quant][graphmode][fx][refactor] insert_observer (#47782)
Summary: Pull Request resolved: https://github.com/pytorch/pytorch/pull/47782
Test Plan:
python test/test_quantization.py TestQuantizeFx
Imported from OSS
Reviewed By: supriyar
Differential Revision: D24900305
fbshipit-source-id: b00a90ab85badea7d18ae007cc68d0bcd58ab15c
