LibJS: Make JS::Cell non-copyable and non-movable

Also make the JS::Cell default constructor protected to provove a
compilation error if you tried to allocate a plain cell.

Libraries/LibJS/Runtime/Cell.h

@@ -27,11 +27,15 @@
 #pragma once
 
 #include <AK/Forward.h>
+#include <AK/Noncopyable.h>
 #include <LibJS/Forward.h>
 
 namespace JS {
 
 class Cell {
+    AK_MAKE_NONCOPYABLE(Cell);
+    AK_MAKE_NONMOVABLE(Cell);
+
 public:
     virtual ~Cell() {}
 
@@ -54,6 +58,9 @@ public:
     Heap& heap() const;
     Interpreter& interpreter();
 
+protected:
+    Cell() {}
+
 private:
     bool m_mark { false };
     bool m_live { true };