[SFT] feat: Add LoRA support for SFT (#127)

This PR adds support for LoRA (Low-Rank Adaptation) for efficient model
fine-tuning.

### Changes

1. Added LoRA configuration support in trainer config
2. Modified FSDP wrapping policy to handle LoRA modules
3. Integrated with existing FSDP training infrastructure
4. Added peft dependency
5. Removed unused ring_attn_utils.py

### Features

- Configurable LoRA rank and alpha parameters
- Target module specification for selective adaptation
- Compatible with FSDP sharding strategy

### Testing

Tested with Qwen2.5-0.5B-Instruct model on GSM8K dataset using the
provided example script.

### Dependencies

- Added `peft` package to requirements.txt

This PR is based on commit 902ddbe6 and has been merged with the latest
upstream main branch.

---------

Co-authored-by: Jiayi Pan <i@jiayipan.me>
Co-authored-by: openhands <openhands@all-hands.dev>

requirements.txt

@@ -6,6 +6,7 @@ flash-attn
 hydra-core
 numpy
 pandas
+peft
 pybind11
 ray
 tensordict<0.6