Introduce another way to escape mapping (other than I())

For arrayOk attributes like marker.size, using I() doesn't always do what you want because I() has dual meaning -- it says prevent mapping and also make sure it converts to JSON as an array.

For example,

plot_ly(x = 1:40, y = 1:40, size = I(30))

Perhaps we could export a function, like i() or something, that prevents mappings, but doesn't add the "AsIs" class.

首先复现带有 marker.size 等 arrayOk 属性的 plot_ly 示例，然后追踪 I() 如何阻止映射并添加 AsIs 类。当一个已导出的替代方案能够阻止映射而不添加 AsIs，同时 I() 保留其现有的双重行为时，此更改就完成了。