[Predicive Back] Unify backpressed behaviour for different platforms.

@hunterstich is already working on this.

Since Jul 6, 2023.

Currently we intercept back gesture through MaterialBackOrchestrator, but it is no-op below API 33 since we have no OnBackInvokedDispatcher on these platforms.
What about convert to use OnBackPressedCallback(from androidx: activity)
We find the activity with such code
private Activity getActivity() {
Context context = getContext();
while (context instanceof ContextWrapper) {
if (context instanceof Activity) {
return (Activity)context;
}
context = ((ContextWrapper)context).getBaseContext();
}
return null;
}
And try cast it to ComponentActivity then get the OnBackPressedDispatcher.

Otherwise, it is very inelegant to handle it separately on the app side for API32 and below platforms.