[nnc] ported conv2d lowering over (#56875)
Summary: Pull Request resolved: https://github.com/pytorch/pytorch/pull/56875
Test Plan: Imported from OSS
Reviewed By: ZolotukhinM
Differential Revision: D28213450
Pulled By: Chillee
fbshipit-source-id: bacdcec83ec61aba1d55f5e3a16f81d6ada3cff2
