Use a different map to distinguish eval contexts

test/mjsunit/regress/regress-5295.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.
+
+eval('var x; let y; ()=>y');
+assertEquals(undefined, x);
+
+function foo() {
+  eval('var z = 1; let w; ()=>w');
+  return z;
+}
+assertEquals(1, foo());
+
+// Multiply nested eval hoisting works
+
+eval('let a; ()=>a; eval("let b; ()=>b; var c")');
+assertEquals(undefined, c);