APP 模式移动端折叠导航 icon 不显示， 期望可以提供APP模式下的面包屑导航开关。

#### 描述问题：
使用JSSDK APP模式，在移动端场景下，折叠菜单按钮显示不正确。

https://github.com/baidu/amis/blob/844b98f09e7c6294e82d156d029715cbd07a707d/src/renderers/App.tsx#L234

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这个按钮样式没办法正常显示。 建议修改为 fas fa-bars

#### 面包屑导航开关

当前默认打开面包屑导航，期望可以通过pages属性配置来关闭或开启面包屑导航。
https://github.com/baidu/amis/blob/844b98f09e7c6294e82d156d029715cbd07a707d/src/renderers/App.tsx#L368

Start by reading src/renderers/App.tsx at the referenced lines around 234 and 368. Confirm how the mobile collapse icon is rendered and how the pages property is handled; done means the icon displays in APP mode and the breadcrumb navigation can be enabled or disabled through pages configuration.

Written by the indexing model from the issue text.