GHSA-h668-6x6g-f8r5: tract: Arbitrary file read via unsanitized ONNX external_data `location` (path traversal) on model load in tract-onnx

The tract-onnx library (a Rust crate for running neural network models) has a vulnerability where it loads external data files referenced in ONNX models without checking the file paths. A malicious model can use absolute paths (like `/etc/passwd`) or directory traversal sequences (like `../../../../etc/passwd`) in the `location` field to trick tract into reading arbitrary files on the system and exposing their contents in the model's output. This is a path-traversal vulnerability (a type of attack where an attacker manipulates file paths to access files outside the intended directory).