[nnc] Add LoopNest::unsafe_fuseLoops to let users apply fusion on stmts that may violate our correctness checks (#60601)
Summary: Pull Request resolved: https://github.com/pytorch/pytorch/pull/60601
Test Plan: Imported from OSS
Reviewed By: navahgar
Differential Revision: D29346128
Pulled By: huiguoo
fbshipit-source-id: 0eb143e97dc57224adeedf99981036ad836e5a03
