[turbofan] Rename context stack as part of the environment for OSR.

test/mjsunit/compiler/osr-block-scope.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.
+
+// Flags: --allow-natives-syntax --use-osr --turbo-osr
+
+"use strict";
+
+function foo() {
+  var result;
+  {
+    let sum = 0;
+    for (var i = 0; i < 100; i++) {
+      if (i == 50) %OptimizeOsr();
+      sum += i;
+    }
+    result = sum;
+  }
+  return result;
+}
+
+assertEquals(4950, foo());
+assertEquals(4950, foo());
+assertEquals(4950, foo());
+
+function bar() {
+  var result;
+  {
+    let sum = 0;
+    for (let i = 0; i < 90; i++) {
+      sum += i;
+      if (i == 45) %OptimizeOsr();
+    }
+    result = sum;
+  }
+  return result;
+}
+
+assertEquals(4005, bar());
+assertEquals(4005, bar());
+assertEquals(4005, bar());