Revert "inductor: remove conv_bn folding from pre_grad pass (#106686)"
This reverts commit 22bc08da29ca8900ff877bb8a20f8369894c4c68.
Reverted https://github.com/pytorch/pytorch/pull/106686 on behalf of https://github.com/XiaobingSuper due to Has big accuracy drop for internal models test ([comment](https://github.com/pytorch/pytorch/pull/106686#issuecomment-1690972043))
