[ONNX] ListUnpack on dynamic tensor list (#56592) (#57603)
Summary:
Pull Request resolved: https://github.com/pytorch/pytorch/pull/57603
With explicit list unpack code from user, it is possible to observe `prim::ListUnpack` with a `ONNX::Sequence` object.
This PR supports the conversion.
Test Plan: Imported from OSS
Reviewed By: malfet
Differential Revision: D28393527
Pulled By: SplitInfinity
fbshipit-source-id: 1e6234d349b94c97c6ff20880a801433a9a428e9
Co-authored-by: BowenBao <bowbao@microsoft.com>
