Fix layout translation in overlay::Group

This bug produced improper positioning of overlays of elements inside a
`Scrollable`.

native/src/overlay/element.rs

@@ -53,8 +53,14 @@ where
     }
 
     /// Computes the layout of the [`Element`] in the given bounds.
-    pub fn layout(&self, renderer: &Renderer, bounds: Size) -> layout::Node {
-        self.overlay.layout(renderer, bounds, self.position)
+    pub fn layout(
+        &self,
+        renderer: &Renderer,
+        bounds: Size,
+        translation: Vector,
+    ) -> layout::Node {
+        self.overlay
+            .layout(renderer, bounds, self.position + translation)
     }
 
     /// Processes a runtime [`Event`].

native/src/overlay/group.rs

@@ -66,13 +66,15 @@ where
         &self,
         renderer: &Renderer,
         bounds: Size,
-        _position: Point,
+        position: Point,
     ) -> layout::Node {
+        let translation = position - Point::ORIGIN;
+
         layout::Node::with_children(
             bounds,
             self.children
                 .iter()
-                .map(|child| child.layout(renderer, bounds))
+                .map(|child| child.layout(renderer, bounds, translation))
                 .collect(),
         )
     }