Update IoU functions

[glenn-jocher]

Remove box area function and support expandable bbox_iou() calls.

Signed-off-by: Glenn Jocher glenn.jocher@ultralytics.com

🛠️ PR Summary

_{Made with ❤️ by Ultralytics Actions}

🌟 Summary

Optimization of bounding box intersection calculations in YOLOv5.

📊 Key Changes

• Changed .chunk(4, 1) to .chunk(4, -1) to adjust tensor slicing.
• Removed the box_area function and incorporated its calculations directly into the box_iou function.
• Simplified the box intersection calculation by using .unsqueeze and .chunk in a more effective way.

🎯 Purpose & Impact

• 🏃 Accelerates intersection-over-union (IoU) computations - a critical piece for evaluating object detection accuracy.
• 🧼 Cleans up the codebase by eliminating unnecessary functions, making the code cleaner and potentially reducing memory overhead.
• 🛠 Might impact the users by providing a slight performance boost in computing metrics during model training and evaluation.