Filter out some notifications.

- Filter out any notification without title and text
- Filter out ongoing notifications on the default, legacy channel
- Respect notification's badgeIcon param instead of always using
  BADGE_ICON_LARGE (this way we can change the default on system)

Bug: 35097755
Bug: 36150272
Change-Id: If10b663e27a96354fd40a6e0f71e17b250290115