Replace width and height with Widget::size

widget/src/checkbox.rs

@@ -174,12 +174,11 @@ where
         tree::State::new(widget::text::State::<Renderer::Paragraph>::default())
     }
 
-    fn width(&self) -> Length {
-        self.width
-    }
-
-    fn height(&self) -> Length {
-        Length::Shrink
+    fn size(&self) -> Size<Length> {
+        Size {
+            width: self.width,
+            height: Length::Shrink,
+        }
     }
 
     fn layout(