Don't remove overlay views when the rasterizer is being torn down #97679
Description
When FlutterFragment is used, ViewGroup#dispatchDetachedFromWindow is called by the Android framework:
at android.view.ViewGroup.dispatchDetachedFromWindow(ViewGroup.java:3948)
at android.view.ViewGroup.dispatchDetachedFromWindow(ViewGroup.java:3948)
at android.view.ViewGroup.endViewTransition(ViewGroup.java:7194)
at android.support.v4.app.DefaultSpecialEffectsController$4$1.run(DefaultSpecialEffectsController.java:281)
at android.os.Handler.handleCallback(Handler.java:938)
at android.os.Handler.dispatchMessage(Handler.java:99)
at android.os.Looper.loopOnce(Looper.java:201)
at android.os.Looper.loop(Looper.java:288)
at android.app.ActivityThread.main(ActivityThread.java:7842)
at java.lang.reflect.Method.invoke(Native Method)
at com.android.internal.os.RuntimeInit$MethodAndArgsCaller.run(RuntimeInit.java:548)
at com.android.internal.os.ZygoteInit.main(ZygoteInit.java:1003)
However, ViewGroup#dispatchDetachedFromWindow expects no view to be removed from the hierarchy, but some views are actually removed in https://github.com/flutter/engine/blob/65dfc9e3bf1927bf555ffb073ea5e7a9f3607e4d/shell/platform/android/io/flutter/plugin/platform/PlatformViewsController.java#L967.
This causes a method to be called on a null instance.
This was likely started after flutter/engine#28894