LibGfx: Unify Rect, Point, and Size

This commit unifies methods and method/param names between the above
classes, as well as adds [[nodiscard]] and ALWAYS_INLINE where
appropriate. It also renamed the various move_by methods to
translate_by, as that more closely matches the transformation
terminology.

Userland/Libraries/LibWeb/Layout/BlockBox.cpp

@@ -142,7 +142,7 @@ bool BlockBox::handle_mousewheel(Badge<EventHandler>, const Gfx::IntPoint&, unsi
     if (!is_scrollable())
         return false;
     auto new_offset = m_scroll_offset;
-    new_offset.move_by(0, wheel_delta);
+    new_offset.translate_by(0, wheel_delta);
     set_scroll_offset(new_offset);
 
     return true;