feat(testing): add implicit test module

Every test now has an implicit module. It can be configured via `configureModule` (from @angular/core/testing)
to add providers, directives, pipes, ...

The compiler now has to be configured separately via `configureCompiler` (from @angular/core/testing)
to add providers or define whether to use jit.

BREAKING CHANGE:
- Application providers can no longer inject compiler internals (i.e. everything
  from `@angular/compiler). Inject `Compiler` instead. This reflects the
  changes to `bootstrap` for module support (3f55aa609f).
- Compiler providers can no longer be added via `addProviders` / `withProviders`.
  Use the new method `configureCompiler` instead.
- Platform directives / pipes need to be provided via
  `configureModule` and can no longer be provided via the
  `PLATFORM_PIPES` / `PLATFORM_DIRECTIVES` tokens.
- `setBaseTestProviders()` was renamed into `initTestEnvironment` and 
  now takes a `PlatformRef` and a factory for a
  `Compiler`.
- E.g. for the browser platform:
  
  BEFORE:
  ```
  import {setBaseTestProviders} from ‘@angular/core/testing’;
  import {TEST_BROWSER_DYNAMIC_PLATFORM_PROVIDERS,
      TEST_BROWSER_DYNAMIC_APPLICATION_PROVIDERS} from ‘@angular/platform-browser-dynamic/testing’;
  
  setBaseTestProviders(TEST_BROWSER_DYNAMIC_PLATFORM_PROVIDERS,
      TEST_BROWSER_DYNAMIC_APPLICATION_PROVIDERS);   
  ```

  AFTER:
  ```
  import {setBaseTestProviders} from ‘@angular/core/testing’;
  import {browserTestCompiler, browserDynamicTestPlatform,
      BrowserDynamicTestModule} from ‘@angular/platform-browser-dynamic/testing’;
  
  initTestEnvironment(
      browserTestCompiler,
      browserDynamicTestPlatform(),
      BrowserDynamicTestModule);

  ```
- E.g. for the server platform:
  
  BEFORE:
  ```
  import {setBaseTestProviders} from ‘@angular/core/testing’;
  import {TEST_SERVER_PLATFORM_PROVIDERS,
      TEST_SERVER_APPLICATION_PROVIDERS} from ‘@angular/platform-server/testing/server’;
  
  setBaseTestProviders(TEST_SERVER_PLATFORM_PROVIDERS,
      TEST_SERVER_APPLICATION_PROVIDERS);   
  ```

  AFTER:
  ```
  import {setBaseTestProviders} from ‘@angular/core/testing’;
  import {serverTestCompiler, serverTestPlatform,
      ServerTestModule} from ‘@angular/platform-browser-dynamic/testing’;
  
  initTestEnvironment(
      serverTestCompiler,
      serverTestPlatform(),
      ServerTestModule);

  ```

Related to #9726
Closes #9846

modules/@angular/core/testing/testing_internal.ts

@@ -110,7 +110,7 @@ export function beforeEachProviders(fn: any /** TODO #9100 */): void {
   jsmBeforeEach(() => {
     var providers = fn();
     if (!providers) return;
-    testInjector.addProviders(providers);
+    testInjector.configureModule({providers: providers});
   });
 }
 
@@ -135,11 +135,10 @@ function _it(jsmFn: Function, name: string, testFn: Function, testTimeOut: numbe
       provide: AsyncTestCompleter,
       useFactory: () => {
         // Mark the test as async when an AsyncTestCompleter is injected in an it()
-        if (!inIt) throw new Error('AsyncTestCompleter can only be injected in an "it()"');
         return new AsyncTestCompleter();
       }
     };
-    testInjector.addProviders([completerProvider]);
+    testInjector.configureModule({providers: [completerProvider]});
     runner.run();
 
     inIt = true;