Pass touch events to embedded Android views with dispatchTouchEvents.

Was previously calling onTouchEvent directly which doesn't make the
event go through the full pipeline (e.g onInterceptTouchEvent is not
called).

shell/platform/android/io/flutter/plugin/platform/PlatformViewsController.java

@@ -243,7 +243,7 @@ public class PlatformViewsController implements MethodChannel.MethodCallHandler
                 flags
         );
 
-        view.onTouchEvent(event);
+        view.dispatchTouchEvent(event);
         result.success(null);
     }