[Feature Request]Tree组件设置disabled后标题添加禁用样式&细分disabled属性

[Exrick]

What problem does this feature solve?

• 目前ViewUI不显示复选框后设置disabled后无禁用样式标识，用户无法区别

https://run.iviewui.com/evJ4Um15

可细分disabled属性禁用复选框或item

https://ant.design/components/tree-cn/

https://www.naiveui.com/zh-CN/light/components/tree

What does the proposed API look like?

新增checkboxDisabled属性

disabled属性增加禁用样式

color: var(--color-disabled);
cursor: not-allowed;

参考Ant Design https://ant.design/components/tree-cn/ 参考Naive UI https://www.naiveui.com/zh-CN/light/components/tree