Fix constant propagation pass issue for onnx.Gather op.

[negiyas]

Fix constant propagation pass issue for onnx.Gather op.
Current constant propagation pass does not work for onnx.Gather with unranked indices (e.g. Tensor).
This PR stops constant propagation with the case.

[X] Prepare LIT test to check errors

onnx-mlir: ./src/Dialect/ONNX/ElementsAttr/DisposableElementsAttr.hpp.inc:75: onnx_mlir::ArrayBuffer<X> mlir::DisposableElementsAttr::getArray() const [with X = long int]: Assertion `onnx_mlir::toBType<X> == getBType() && “X must match element type”‘ failed.

[sorenlassen]

actually, I think the real problem is that the const prop implementation only works for int64 indices and not int32, sorry about that

rank 0 indices seems to work fine for int64

please see the alternative fix in PR #2488

[negiyas]

@sorenlassen Your comments are right. I am closing this PR. Thank you for your comments.