Update train, val tqdm to fixed width

[glenn-jocher]

Attempt to solve #2685 (result: does not solve issue)

Attempting https://stackoverflow.com/questions/41707229/tqdm-printing-to-newline

🛠️ PR Summary

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🌟 Summary

Improved progress bar formatting and terminal size adaptation for training and validation scripts.

📊 Key Changes

• Added NCOLS variable to manage progress bar length dynamically according to terminal window size.
• Modified progress bar in train.py and val.py to use the new NCOLS setting, which adjusts to the terminal width.
• Improvement to the progress bar formatting to make it look consistent across different terminal sizes.

🎯 Purpose & Impact

• These changes aim to enhance the user interface by ensuring progress bars during training and validation are sized appropriately for the user's terminal, improving readability and aesthetics. 🖥️
• Users will benefit from a cleaner, more responsive output that adapts to various terminal environments. This can be particularly helpful for those running YOLOv5 on remote servers or containers where terminal dimensions can vary. 📈
• The main impact is on the user experience; there's no change to the underlying machine learning or inference functionalities. 🚀

[glenn-jocher]

/rebase

[glenn-jocher]

/rebase