Update check_requirements() single install

[glenn-jocher]

Faster install and better conflict resolution with single installation

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

🛠️ PR Summary

_{Made with ❤️ by Ultralytics Actions}

🌟 Summary

This PR simplifies dependency checks and improves auto-update functionality in the Ultralytics YOLOv5 repository.

📊 Key Changes

• Altered check_requirements function usage from requiring a tuple to a string for single package requirements.
• Refined the way check_requirements handles package installation and error messaging.
• Updated various files to use the new string input for single package checks.
• Simplified the conditionals in check_requirements for handling different input types (path, list, string).

🎯 Purpose & Impact

• Streamlined Code: Simplifies code by allowing single package names as strings rather than one-item tuples, making it clearer and cleaner.
• Enhanced Auto-Update: Better handling of auto-updates for missing packages, providing a smoother user experience when dependencies are not met.
• Clearer Messaging: Users receive more informative messages when packages are missing or automatically updated, reducing confusion and aiding in troubleshooting.