[MM-39839] Changes for writing unit tests, some re-org (#1849)

* Move tests to individual folders

* Moved e2e tests to e2e folder, fixed lint issues

* Lint fix

e2e/modules/utils.js

@@ -0,0 +1,15 @@
+// Copyright (c) 2015-2016 Yuya Ochiai
+// Copyright (c) 2016-present Mattermost, Inc. All Rights Reserved.
+// See LICENSE.txt for license information.
+
+function asyncSleep(timeout) {
+    return new Promise((resolve) => {
+        setTimeout(() => {
+            resolve();
+        }, timeout);
+    });
+}
+
+module.exports = {
+    asyncSleep,
+};