Reland of [stubs] Port KeyedLoadIC_Generic stub to TurboFan

test/mjsunit/keyed-load-generic.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.
+
+// Flags: --allow-natives-syntax
+
+(function NegativeIndexAndDictionaryElements() {
+  function f(o, idx) {
+    return o[idx];
+  }
+
+  f({}, 0);
+  f({}, 0);  // Make the IC megamorphic/generic.
+
+  var o = {};
+  o[1000000] = "dictionary";
+  var c = -21;
+  o[c] = "foo";
+  assertEquals("foo", f(o, c));
+})();