Move `analyzer_cli` into the SDK.

pkg/analyzer_cli/test/data/super_mixin_example.dart

 // Copyright (c) 2015, the Dart project authors.  Please see the AUTHORS file
 // for details. All rights reserved. Use of this source code is governed by a
 // BSD-style license that can be found in the LICENSE file.
 
-import "package:expect/expect.dart";
+/// This produces errors normally, but --supermixin disables them.
+class Test extends Object with C {
+  void foo() {}
+}
 
-class A {
-  call({a: 42}) {
-    return 499 + a;
+abstract class B {
+  void foo();
+}
+
+abstract class C extends B {
+  void bar() {
+    super.foo();
   }
 }
-
-main() {
-  Expect.equals(497, Function.apply(new A(), [], {#a: -2}));
-}