refactor(common): CleanUp HttpClient's imports (#18120)

PR Close #18120

packages/common/http/src/client.ts

@@ -17,7 +17,7 @@ import {HttpHandler} from './backend';
 import {HttpHeaders} from './headers';
 import {HttpParams} from './params';
 import {HttpRequest} from './request';
-import {HttpEvent, HttpEventType, HttpResponse} from './response';
+import {HttpEvent, HttpResponse} from './response';
 
 
 /**

packages/common/http/src/interceptor.ts

@@ -11,7 +11,7 @@ import {Observable} from 'rxjs/Observable';
 
 import {HttpHandler} from './backend';
 import {HttpRequest} from './request';
-import {HttpEvent, HttpResponse} from './response';
+import {HttpEvent} from './response';
 
 /**
  * Intercepts `HttpRequest` and handles them.

packages/common/http/src/jsonp.ts

@@ -12,7 +12,6 @@ import {Observable} from 'rxjs/Observable';
 import {Observer} from 'rxjs/Observer';
 
 import {HttpBackend, HttpHandler} from './backend';
-import {HttpInterceptor} from './interceptor';
 import {HttpRequest} from './request';
 import {HttpErrorResponse, HttpEvent, HttpEventType, HttpResponse} from './response';
 

packages/common/http/src/module.ts

@@ -6,7 +6,7 @@
  * found in the LICENSE file at https://angular.io/license
  */
 
-import {Inject, ModuleWithProviders, NgModule, Optional, forwardRef} from '@angular/core';
+import {Inject, ModuleWithProviders, NgModule, Optional} from '@angular/core';
 
 import {HttpBackend, HttpHandler} from './backend';
 import {HttpClient} from './client';

packages/common/http/src/response.ts

@@ -6,9 +6,6 @@
  * found in the LICENSE file at https://angular.io/license
  */
 
-import {Observable} from 'rxjs/Observable';
-import {empty} from 'rxjs/observable/empty';
-
 import {HttpHeaders} from './headers';
 
 /**