Messaging: Implement per conversation channels. Update API level to 28.

* Get rid of in-app settings for notifications, replaced by channels features
* Remove all the notification plumbing and dead code

Test: m, manual

Signed-off-by: Luca Stefani <luca.stefani.ge1@gmail.com>
Signed-off-by: Joey <joey@lineageos.org>
Signed-off-by: Danny Baumann <dannybaumann@web.de>
Signed-off-by: Arne Coucheron <arco68@gmail.com>
Signed-off-by: Lyubo <lyubodzhamov@gmail.com>
Change-Id: Idb39ca32751d40b3376934775d2119dd6cc7e297

src/com/android/messaging/datamodel/NotificationState.java

@@ -134,15 +134,6 @@ public abstract class NotificationState {
      */
     public abstract int getPriority();
 
-    /** @return custom ringtone URI or null if not set */
-    public String getRingtoneUri() {
-        return null;
-    }
-
-    public boolean getNotificationVibrate() {
-        return false;
-    }
-
     public long getLatestReceivedTimestamp() {
         return Long.MIN_VALUE;
     }