feat(test): allow tests to specify the platform and application providers used

With providers split into bundles, the test injector is now able to
use providers for a given bundle. Suggested provider lists for tests are
available in `angular2/platform/testing/<platform>`.

Change the providers for a test suite using `setBaseTestProviders`. This
should be done once at the start of the test suite, before any test cases
run.

BREAKING CHANGE: Tests are now required to use `setBaseTestProviders`
to set up. Assuming your tests are run on a browser, setup would change
as follows.

Before:

```js
// Somewhere in test setup
import {BrowserDomAdapter} from 'angular2/src/platform/browser/browser_adapter';
BrowserDomAdapter.makeCurrent
```

After:

```js
// Somewhere in the test setup
import {setBaseTestProviders} from 'angular2/testing';
import {
  TEST_BROWSER_PLATFORM_PROVIDERS,
  TEST_BROWSER_APPLICATION_PROVIDERS
} from 'angular2/platform/testing/browser';

setBaseTestProviders(TEST_BROWSER_PLATFORM_PROVIDERS,
                     TEST_BROWSER_APPLICATION_PROVIDERS);
```

Closes #5351, Closes #5585

Closes #5975

modules_dart/angular2_testing/lib/angular2_testing.dart

@@ -5,12 +5,12 @@ import 'package:test/test.dart';
 import 'package:angular2/angular2.dart';
 import 'package:angular2/src/core/di/metadata.dart' show InjectMetadata;
 import 'package:angular2/src/core/di/exceptions.dart' show NoAnnotationError;
-import 'package:angular2/platform/browser_static.dart' show BrowserDomAdapter;
 import 'package:angular2/src/core/reflection/reflection.dart';
 import 'package:angular2/src/core/reflection/reflection_capabilities.dart';
 import 'package:angular2/src/testing/test_injector.dart';
 export 'package:angular2/src/testing/test_component_builder.dart';
 export 'package:angular2/src/testing/test_injector.dart' show inject;
+import 'package:angular2/platform/testing/browser.dart';
 
 /// One time initialization that must be done for Angular2 component
 /// tests. Call before any test methods.
@@ -24,8 +24,8 @@ export 'package:angular2/src/testing/test_injector.dart' show inject;
 /// }
 /// ```
 void initAngularTests() {
-  BrowserDomAdapter.makeCurrent();
   reflector.reflectionCapabilities = new ReflectionCapabilities();
+  setBaseTestProviders(TEST_BROWSER_PLATFORM_PROVIDERS, TEST_BROWSER_APPLICATION_PROVIDERS);
 }
 
 void _addTestInjectorTearDown() {