[ONNX] Add eliminate_unused_items pass (#38812)
Summary:
This PR:
- Adds eliminate_unused_items pass that removes unused inputs and initializers.
- Fixes run_embed_params function so it doesn't export unnecessary parameters.
- Removes test_modifying_params in test_verify since it's no longer needed.
Pull Request resolved: https://github.com/pytorch/pytorch/pull/38812
Reviewed By: ezyang
Differential Revision: D22236416
Pulled By: houseroad
fbshipit-source-id: 30e1a6e8823a7e36b51ae1823cc90476a53cd5bb
