Revert "Move `analyzer_cli` into the SDK."

pkg/analyzer_cli/test/data/packages_file/sdk_ext_user.dart

Index: pkg/analyzer_cli/test/data/packages_file/sdk_ext_user.dart
diff --git a/pkg/analyzer_cli/test/data/packages_file/sdk_ext_user.dart b/pkg/analyzer_cli/test/data/packages_file/sdk_ext_user.dart
deleted file mode 100644
index b346f7f1ed19a53ff94321f5a12737f3decde69f..0000000000000000000000000000000000000000
--- a/pkg/analyzer_cli/test/data/packages_file/sdk_ext_user.dart
+++ /dev/null
@@ -1,10 +0,0 @@
-// 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 'dart:foo';
-
-main() {
-  // import of 'dart:foo' should resolve to a file which defines bar().
-  bar();
-}