Remove usage of mattermost-redux from Cypress (#24652)

* Remove usage of mattermost-redux from Cypress

* Add Webpack preprocessor for Cypress

e2e-tests/cypress/tests/support/client-impl.js

@@ -1,7 +1,7 @@
 // Copyright (c) 2015-present Mattermost, Inc. All Rights Reserved.
 // See LICENSE.txt for license information.
 
-import Client4 from 'mattermost-redux/client/client4';
+import {Client4} from '@mattermost/client';
 
 import clientRequest from '../plugins/client_request';