[quant][graphmode] quantization work for prim::If (#34518)
Summary: Pull Request resolved: https://github.com/pytorch/pytorch/pull/34518
Test Plan:
python test/test_jit.py
Imported from OSS
Differential Revision: D20519606
fbshipit-source-id: 94d49e18d97df642cbcb446df12376f6d2a397bc
