[ColossalChat][WIP] Refactor coati; Fix PPO, LORA; Add DPO

[YeAnbang]

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📝 What does this PR do?

• Refactor coati
• Fix PPO, LORA
• Add DPO
• Adopt ColossalChat conversation format
• Upgrade acceleration methods. Use Plugin and Boosters
• Support tensor parallelism
• Adopt ColossalChat conversation format
• Fix tests

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• I have performed a self-review of my code
• I have added thorough tests.
• I have added docstrings for all the functions/methods I implemented

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[YeAnbang]

Not ready for review. Thanks