Fix VM memory allocation optimizations by reducing what we allocate on the heap

internal/object/hash.go

@@ -12,7 +12,7 @@ type HashKey struct {
 	Value uint64
 }
 
-func (b *Boolean) HashKey() HashKey {
+func (b Boolean) HashKey() HashKey {
 	var value uint64
 
 	if b.Value {
@@ -24,11 +24,11 @@ func (b *Boolean) HashKey() HashKey {
 	return HashKey{Type: b.Type(), Value: value}
 }
 
-func (i *Integer) HashKey() HashKey {
+func (i Integer) HashKey() HashKey {
 	return HashKey{Type: i.Type(), Value: uint64(i.Value)}
 }
 
-func (s *String) HashKey() HashKey {
+func (s String) HashKey() HashKey {
 	h := fnv.New64a()
 	h.Write([]byte(s.Value))
 
@@ -98,7 +98,7 @@ func (h *Hash) Get(index Object) (Object, error) {
 
 	pair, found := h.Pairs[key.HashKey()]
 	if !found {
-		return &Null{}, nil
+		return Null{}, nil
 	}
 
 	return pair.Value, nil