Make direct-reply notification as HUN in EditTextVariations

Also, set the content intent to launch an editorActivity as the message
notifiation when tapping the notification.

Bug: 190057993
Test: make EditTextVariations, manual test by using EditTextVariations
      app to simulate the issue step.
Change-Id: I1a4463dc44031eaebb286ad2a289870e97a1c475