Add "STOP" option during visualization

There's a START option to start the algorithm but there is no option to stop in between. So add the STOP option so that the user can stop the algorithm after the desired iteration and see the progress in sorting at any particular instance.

未指定文件或测试；首先定位创建 START 选项的 GUI 代码，以及它触发的排序循环。跟踪一次迭代如何更新可视化效果，然后添加一个 STOP 控件，使其完成的行为是算法停止，并且当前的排序进度保持可见。

由索引模型根据 Issue 内容生成。