Feature description

Implement the ONNX Scatter operation in the burn-import crate, mapping ONNX's Scatter semantics into Burn. The goal is to ensure that models using the Scatter op can be imported and run smoothly in Burn.

Feature motivation

Scatter is available in Burn but not in burn-import. This is a common operation required for efficient tensor manipulation and indexing in modern ONNX models.

(Optional) Suggest a Solution

• Replicate the approach taken by other indexing-related ops (e.g., Gather) currently implemented in burn-import.
• Add robust testing for various shapes and indices.

For more information:

• Consult the SUPPORTED-ONNX-OPS.md.
• Use the contributor book for implementation details.
• See the main tracking issue Help Wanted: Implementing ONNX Ops #1714.

Related context: #1714