refactor(testing): introduce new testing api to support ng modules

BREAKING CHANGE:
- deprecations:
  * `withProviders`, use `TestBed.withModule` instead
  * `addProviders`, use `TestBed.configureTestingModule` instead
  * `TestComponentBuilder`, use `TestBed.configureTestModule` / `TestBed.override...` / `TestBed.createComponent` instead.

Closes #10354

modules/@angular/compiler/core_private_testing.ts

@@ -0,0 +1,15 @@
+/**
+ * @license
+ * Copyright Google Inc. All Rights Reserved.
+ *
+ * Use of this source code is governed by an MIT-style license that can be
+ * found in the LICENSE file at https://angular.io/license
+ */
+
+import {__core_private_testing__ as r, __core_private_testing_types__ as t} from '@angular/core/testing';
+
+export type TestingCompiler = t.TestingCompiler;
+export var TestingCompiler: typeof t.TestingCompiler = r.TestingCompiler;
+
+export type TestingCompilerFactory = t.TestingCompilerFactory;
+export var TestingCompilerFactory: typeof t.TestingCompilerFactory = r.TestingCompilerFactory;