LibGfx: Add Point::scaled(T) and Rect::scaled(T)

Note that we already have Size::scaled(T). While subjectively providing
API symmetry, this is mostly to allow using these methods in templated
helpers without caring what the exact underlying type is.

Userland/Libraries/LibGfx/Point.h

@@ -91,6 +91,13 @@ public:
         return point;
     }
 
+    [[nodiscard]] Point<T> scaled(T dboth) const
+    {
+        Point<T> point = *this;
+        point.scale_by(dboth);
+        return point;
+    }
+
     [[nodiscard]] Point<T> scaled(Point<T> const& delta) const
     {
         Point<T> point = *this;