[applications/ColossalChat/examples/training_scripts/lora_finetune.py]: Fixed bug, added save_interval and added auto resume functions

[bbbolt]

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📝 What does this PR do?

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1. Fix the gradient not enabled bug during lora fine-tuning, by adding the code "model.enable_input_require_grads()".
2. Add interval save function for lora and optimizer state, controled by save_interval argument
3. Add auto resume function, controled by lora_path and optmizer_path arguments.
   if you have any plots/diagrams/screenshots/tables, please attach them here.

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[bbbolt]

fix the format