[shared engine] Consider letting developers take over life cycle events in add-to-app scenarios if they want #94702
Description
The current life cycle of AppLifecycleState is associated with the life cycle of FlutterActivity/FlutterViewController.
It seems that because we did not consider the add-to-app scenario when it was originally designed.
But in an add-to-app scenario, this may not work. This is because the application may have multiple FlutterViewController/FlutterActivity, and they share one FlutterEngine.
The wrong setting of AppLifecycleState may cause the frame to fail to be scheduled and rendered correctly.
So I guess we can provide a option to developers to let them take over life cycle events if they want. If so, flutter will no longer send life cycle events, but let developers send life cycle events themselves.
related issue:
#52456
/cc @gaaclarke @blasten