unsetFlutterBoost用法

为了节省内存占用，我想要做一个事情，就是app进入后台，如果没有flutter相关的页面，我就调用unsetFlutterBoost，以释放内存。
进前后之后，在调用setup进行初始化，不知道是否可以

Start by reviewing the unsetFlutterBoost and setup lifecycle APIs and how they behave when the app enters and leaves the background. Determine whether FlutterBoost can be safely torn down and initialized again when no Flutter pages remain; document the supported behavior or define the required lifecycle change and its completion criteria.

Written by the indexing model from the issue text.