[ONNX] Update special post process for SequenceInsert after SequenceEmpty (#56965) (#58693)
Summary:
Pull Request resolved: https://github.com/pytorch/pytorch/pull/58693
`ONNX::SequenceEmpty` requires dtype to be provided, and is default to float. We updates previous dtype of created `ONNX::SequenceEmpty` node when dtype is later discovered to be other than float, through downstream `ONNX::SequenceInsert` node. This PR improves the algorithm to cover nested loop case.
Test Plan: Imported from OSS
Reviewed By: driazati
Differential Revision: D28714808
Pulled By: SplitInfinity
fbshipit-source-id: e45ab3a12d0fec637733acbd3cd0438ff80d2cd4
Co-authored-by: BowenBao <bowbao@microsoft.com>
