Add bundle dismissal reason

Test: NotificationManagerServiceTest
Test: NotifCollectionTest
Test: view event log after swiping away a bundle
Flag: android.app.notification_classification_ui
Flag: android.service.notification.nm_classification_nls
Fixes: 416144530
Change-Id: Idc8e64f3b83febb70c4fc6c88252a31be1dd033a