Optimize Model Path Management

[JingofXin]

Model-related paths are uniformly determined and managed by ModelManager:
1. Creation of model paths that appear in its subclass ModuleBase;
2. The original file path of the model, the LoRA storage path, the merge storage path, and the root storage path are all unified under ModelManager;
3. Version control of fine-tuned models.

[wzh1994]

add documents