[Train] Support DP in training

[Musisoul]

No description provided.

[gemini-code-assist]

Code Review

This pull request introduces support for Data Parallel (DDP) training, including a new configuration and script for Qwen Image LoRA training, a custom LightX2VDistributedDataParallel wrapper, and integration into the base and DMD trainers. The code review identified several critical and high-severity issues in the DDP wrapper implementation: overriding class breaks isinstance checks in is_ddp_module (disabling proper gradient synchronization), and accessing non-standard attributes like find_unused_parameters on the DDP instance will cause runtime crashes. Additionally, the review suggests improving the robustness of attribute access and delegation in the wrapper by avoiding fragile super().getattr('module') calls and generalizing setattr beyond the hardcoded block_mask attribute.

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