[NNC] make inlining immediate (take 3) (#44231)
Summary:
This is a reup https://github.com/pytorch/pytorch/issues/43885 with an extra commit which should fix the bugs that caused it to be reverted. Read that for general context.
The issue here was that we were still using the side maps `tensor_to_stmt_` and `stmt_to_tensor_` which get invalidated by any transform of the IR (rather than just any transform that isn't computeInline). I added a comment about this but didn't actually address our usages of it.
I've removed these maps and changed the `getLoopBodyFor` and `getLoopStatementsFor` helpers to search the root stmt directly.
Pull Request resolved: https://github.com/pytorch/pytorch/pull/44231
Reviewed By: albanD
Differential Revision: D23689688
Pulled By: nickgg
fbshipit-source-id: 1c6009a880f8c0cebf2300fd06b5cc9322bffbf9
