Fix detaching views rendered under header config component. (#282)

This change fixes the problem when header update would get triggered while the header config subviews are not yet fully unmounted. The root cause of this problem is kind of a mystery, I encouneter a crash when going back using back button from a screen that have custom back button image rendered. Turned out that after implementing removeAll schema the problem no longer occurs. I didn't have enough time to investigate it further but supporting removeAll schema is an improvement regardless so going with this solution for now.

android/src/main/java/com/swmansion/rnscreens/ScreenStackHeaderConfigViewManager.java

@@ -32,6 +32,11 @@ public class ScreenStackHeaderConfigViewManager extends ViewGroupManager<ScreenS
     parent.addConfigSubview((ScreenStackHeaderSubview) child, index);
   }
 
+  @Override
+  public void removeAllViews(ScreenStackHeaderConfig parent) {
+    parent.removeAllConfigSubviews();
+  }
+
   @Override
   public void removeViewAt(ScreenStackHeaderConfig parent, int index) {
     parent.removeConfigSubview(index);