Add test cases for AWS Cloud Admin Setting forms (Notification)

Problem/Motivation

 Add the following three test cases for AWS Cloud Admin Setting forms:

• Drupal\Tests\aws_cloud\Functional\Config\AwsCloudAdminSettings::testAwsCloudAdminLocationSettings()
• Drupal\Tests\aws_cloud\Functional\Config\AwsCloudAdminSettings::testAwsCloudAdminNotificationSettings() (this issue)
• Drupal\Tests\aws_cloud\Functional\Config\AwsCloudAdminSettings::testAwsCloudAdminSettings()

Here is the assertions in each form:

• Display a form and assert if HTTP response 200 is returned (Please see also the existing utility methods for testing: CloudAssertionTrait)
• Assert if there is no warning or error status messages (Please see also the existing utility methods for testing: CloudAssertionTrait)
• Input some value of the fields and click Save and make sure the input values are correctly stored

Specification:

• Implement createAdminSettingsNotificationsTestFormData() to return an array including the random input data for /admin/config/services/cloud/aws_cloud/notification
• Access (HTTP Get) /admin/config/services/cloud/aws_cloud/notification and post the random input data.