Rect: Add set_right_without_resize() and set_bottom_without_resize()

Sometimes you want to move the Rect by its right or bottom edge without
resizing the rect in the process. There are probably better names for
this but nothing comes to mind at the moment.

Libraries/LibDraw/Rect.h

@@ -192,6 +192,18 @@ public:
         set_height(bottom - y() + 1);
     }
 
+    void set_right_without_resize(int new_right)
+    {
+        int delta = new_right - right();
+        move_by(delta, 0);
+    }
+
+    void set_bottom_without_resize(int new_bottom)
+    {
+        int delta = new_bottom - bottom();
+        move_by(0, delta);
+    }
+
     bool intersects(const Rect& other) const
     {
         return left() <= other.right()