[deoptimizer] Materialize array iterators in the deoptimizer.

test/mjsunit/regress/regress-681383.js

+// Copyright 2017 the V8 project authors. All rights reserved.
+// Use of this source code is governed by a BSD-style license that can be
+// found in the LICENSE file.
+
+// Flags: --allow-natives-syntax
+
+function f(deopt) {
+  let array = [42];
+  let it = array[Symbol.iterator]();
+  if (deopt) {
+    %_DeoptimizeNow();
+    return it.next().value;
+  }
+}
+
+f(false);
+f(false);
+%OptimizeFunctionOnNextCall(f);
+assertEquals(f(true), 42);