Add plot transform and deprecated wrappers

[SAKURA-CAT]

变更内容

• 新增 swanlab.plot 模块，作为自定义图表的占位入口，目前从 echarts 组件中导出 confusion_matrix、roc_curve、pr_curve
• 为 swanlab.roc_curve()、swanlab.pr_curve()、swanlab.confusion_matrix() 添加 @deprecated 装饰器和弃用警告，引导用户使用 swanlab.echarts.* 替代
• 更新 __init__.pyi 类型存根，添加 plot 导出
• 调整 __all__ 导出顺序，将 echarts 和 plot 归类到数据模块组

变更文件

• swanlab/__init__.py — 添加 plot 导入、deprecated 包装函数
• swanlab/__init__.pyi — 添加 plot 类型导出
• swanlab/sdk/__init__.py — 添加 plot 导入，调整导出顺序
• swanlab/sdk/internal/run/transforms/plot/__init__.py — 新增 plot 模块

[gemini-code-assist]

Code Review

This pull request introduces a new plot module and deprecates the top-level roc_curve, pr_curve, and confusion_matrix functions, redirecting them to the echarts module with appropriate deprecation warnings. The feedback suggests adding stacklevel=2 to the warnings.warn calls to ensure the warning points to the user's code rather than the internal wrapper. Additionally, it is recommended to update the type stub file (__init__.pyi) to include these deprecated functions to maintain consistency and provide better IDE support.