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/compiler-cli/README.md

@@ -49,8 +49,10 @@ bootstrap.ts
 -------------
 
 import {MainModuleNgFactory} from './main_module.ngfactory';
+import {bootstrapModuleFactory} from '@angular/core';
+import {browserPlatform} from '@angular/platform-browser';
 
-MainModuleNgFactory.create(browserPlatform().injector);
+bootstrapModuleFactory(MainModuleNgFactory, browserPlatform());
 ```
 
 ## Configuration

modules/@angular/compiler-cli/integrationtest/test/util.ts

@@ -6,14 +6,14 @@
  * found in the LICENSE file at https://angular.io/license
  */
 
-import {AppModuleFactory, AppModuleRef} from '@angular/core';
+import {AppModuleFactory, AppModuleRef, bootstrapModuleFactory} from '@angular/core';
 import {ComponentFixture} from '@angular/core/testing';
 import {serverPlatform} from '@angular/platform-server';
 
 import {MainModuleNgFactory} from '../src/module.ngfactory';
 
 export function createModule<M>(factory: AppModuleFactory<M>): AppModuleRef<M> {
-  return factory.create(serverPlatform().injector);
+  return bootstrapModuleFactory(factory, serverPlatform());
 }
 
 export function createComponent<C>(