Background

Follow-up from #1921. Move op_configuration.rs from burn-import to onnx-ir to align with ONNX IR structure.

Task

Relocate op_configuration.rs to onnx-ir, ensuring functionality and dependencies are preserved.

Steps

1. Move op_configuration.rs from burn-import/src/ to onnx-ir/src/.
2. Update import paths in all dependent modules to reference onnx-ir.
3. Adjust Cargo.toml in onnx-ir and burn-import as needed.
4. Run cargo test to verify no breaking changes.
5. Update documentation to reflect the new location.

Acceptance Criteria

• op_configuration.rs is in onnx-ir/src/.
• All imports and references are updated.
• Project builds (cargo build) and tests pass (cargo test).
• Documentation is updated.
• No regressions in ONNX model import or node configuration.