LibJS: Make MarkedValueList copyable and move assignable

This is required to store a MarkedValueList as the value of a HashMap.

Userland/Libraries/LibJS/Runtime/ExecutionContext.h

@@ -24,7 +24,7 @@ struct ExecutionContext {
 
     [[nodiscard]] ExecutionContext copy() const
     {
-        ExecutionContext copy { arguments.copy() };
+        ExecutionContext copy { arguments };
 
         copy.function = function;
         copy.realm = realm;

Userland/Libraries/LibJS/Runtime/MarkedValueList.cpp

@@ -10,21 +10,42 @@
 namespace JS {
 
 MarkedValueList::MarkedValueList(Heap& heap)
-    : m_heap(heap)
+    : m_heap(&heap)
 {
-    m_heap.did_create_marked_value_list({}, *this);
+    m_heap->did_create_marked_value_list({}, *this);
+}
+
+MarkedValueList::MarkedValueList(MarkedValueList const& other)
+    : Vector<Value, 32>(other)
+    , m_heap(other.m_heap)
+{
+    m_heap->did_create_marked_value_list({}, *this);
 }
 
 MarkedValueList::MarkedValueList(MarkedValueList&& other)
     : Vector<Value, 32>(move(static_cast<Vector<Value, 32>&>(other)))
     , m_heap(other.m_heap)
 {
-    m_heap.did_create_marked_value_list({}, *this);
+    m_heap->did_create_marked_value_list({}, *this);
 }
 
 MarkedValueList::~MarkedValueList()
 {
-    m_heap.did_destroy_marked_value_list({}, *this);
+    m_heap->did_destroy_marked_value_list({}, *this);
+}
+
+MarkedValueList& MarkedValueList::operator=(JS::MarkedValueList const& other)
+{
+    Vector<Value, 32>::operator=(other);
+
+    if (m_heap != other.m_heap) {
+        m_heap = other.m_heap;
+
+        // NOTE: IntrusiveList will remove this MarkedValueList from the old heap it was part of.
+        m_heap->did_create_marked_value_list({}, *this);
+    }
+
+    return *this;
 }
 
 }

Userland/Libraries/LibJS/Runtime/MarkedValueList.h

@@ -15,26 +15,18 @@
 namespace JS {
 
 class MarkedValueList : public Vector<Value, 32> {
-    AK_MAKE_NONCOPYABLE(MarkedValueList);
-
 public:
     explicit MarkedValueList(Heap&);
+    MarkedValueList(MarkedValueList const&);
     MarkedValueList(MarkedValueList&&);
     ~MarkedValueList();
 
-    MarkedValueList& operator=(MarkedValueList&&) = delete;
-
     Vector<Value, 32>& values() { return *this; }
 
-    MarkedValueList copy() const
-    {
-        MarkedValueList copy { m_heap };
-        copy.extend(*this);
-        return copy;
-    }
+    MarkedValueList& operator=(JS::MarkedValueList const& other);
 
 private:
-    Heap& m_heap;
+    Heap* m_heap;
 
     IntrusiveListNode<MarkedValueList> m_list_node;