Allow lexically declared "arguments" in function scope in sloppy mode.

test/mjsunit/regress/regress-4577.js

 // Copyright 2015 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.
 
 function f(...arguments) {
   return Array.isArray(arguments);
 }
 assertTrue(f());
 
 function g({arguments}) {
   return arguments === 42;
 }
 assertTrue(g({arguments: 42}));
+
+function foo() {
+  let arguments = 2;
+  return arguments;
+}
+assertEquals(2, foo());
+
+assertThrows(function(x = arguments, arguments) {}, ReferenceError);