refactor(core): clean up platform bootstrap and initTestEnvironment

- Introduces `CompilerFactory` which can be part of a `PlatformRef`.
- Introduces `WorkerAppModule`, `WorkerUiModule`, `ServerModule`
- Introduces `serverDynamicPlatform` for applications using runtime compilation
  on the server.
- Changes browser bootstrap for runtime and offline compilation (see below for an example).
  * introduces `bootstrapModule` and `bootstrapModuleFactory` in `@angular/core`
  * introduces new `browserDynamicPlatform` in `@angular/platform-browser-dynamic
- Changes `initTestEnvironment` (which used to be `setBaseTestProviders`) to not take a compiler factory any more (see below for an example).

BREAKING CHANGE:

## Migration from `setBaseTestProviders` to `initTestEnvironment`:

- 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 {initTestEnvironment} from ‘@angular/core/testing’;
  import {browserDynamicTestPlatform,
      BrowserDynamicTestModule} from ‘@angular/platform-browser-dynamic/testing’;

  initTestEnvironment(
      BrowserDynamicTestModule,
      browserDynamicTestPlatform());

  ```
- 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 {initTestEnvironment} from ‘@angular/core/testing’;
  import {serverTestPlatform,
      ServerTestModule} from ‘@angular/platform-browser-dynamic/testing’;

  initTestEnvironment(
      ServerTestModule,
      serverTestPlatform());

  ```

## Bootstrap changes
```
@AppModule({
  modules: [BrowserModule],
  precompile: [MainComponent],
  providers: […], // additional providers
  directives: […], // additional platform directives
  pipes: […] // additional platform pipes
})
class MyModule {
  constructor(appRef: ApplicationRef) {
    appRef.bootstrap(MainComponent);
  }
}

// offline compile
import {browserPlatform} from ‘@angular/platform-browser’;
import {bootstrapModuleFactory} from ‘@angular/core’;

bootstrapModuleFactory(MyModuleNgFactory, browserPlatform());

// runtime compile long form
import {browserDynamicPlatform} from ‘@angular/platform-browser-dynamic’;
import {bootstrapModule} from ‘@angular/core’;

bootstrapModule(MyModule, browserDynamicPlatform());
```

Closes #9922
Part of #9726

modules/@angular/platform-browser/test/browser/bootstrap_spec.ts

@@ -304,7 +304,7 @@ export function main() {
          ])).then((compRef) => {
            expect(el).toHaveText('hello world!');
            expect(compilerConsole.warnings).toEqual([
-             'Passing an instance of XHR to "bootstrap()" as provider is deprecated. Pass the provider to "createCompiler()" and call "bootstrap()" with the created compiler instead.'
+             'Passing an instance of XHR to "bootstrap()" as provider is deprecated. Pass the provider via the new parameter "compilerOptions" of "bootstrap()" instead.'
            ]);
            async.done();
          });

modules/@angular/platform-browser/test/web_workers/worker/renderer_integration_spec.ts

@@ -26,7 +26,7 @@ import {ServiceMessageBrokerFactory_} from '@angular/platform-browser/src/web_wo
 import {CompilerConfig} from '@angular/compiler';
 import {dispatchEvent} from '../../../../platform-browser/testing/browser_util';
 import {BrowserTestModule} from '@angular/platform-browser/testing';
-import {browserTestCompiler, browserDynamicTestPlatform} from '@angular/platform-browser-dynamic/testing'
+import {browserDynamicTestPlatform} from '@angular/platform-browser-dynamic/testing'
 
 export function main() {
   function createWebWorkerBrokerFactory(
@@ -70,7 +70,6 @@ export function main() {
           uiRenderStore = new RenderStore();
           var testUiInjector = new TestInjector();
           testUiInjector.platform = browserDynamicTestPlatform();
-          testUiInjector.compilerFactory = browserTestCompiler;
           testUiInjector.appModule = BrowserTestModule;
           testUiInjector.configureModule({
             providers: [