Reland: [modules] Properly initialize declared variables.

test/mjsunit/modules-init3.js

+// Copyright 2016 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.
+//
+// MODULE
+
+import {check} from "modules-skip-init3.js";
+
+assertSame(undefined, w);
+assertThrows(() => x, ReferenceError);
+assertThrows(() => y, ReferenceError);
+assertThrows(() => z, ReferenceError);
+
+export function* v() { return 40 }
+export var w = 41;
+export let x = 42;
+export class y {};
+export const z = "hello world";
+
+assertTrue(check());