Use a separate notification id for failure notifications

This way failure notifications won't overwrite the existing chat notifications (if there are any) as they also use thread id as notification id

app/src/main/kotlin/com/simplemobiletools/smsmessenger/helpers/NotificationHelper.kt

@@ -119,7 +119,7 @@ class NotificationHelper(private val context: Context) {
     fun showSendingFailedNotification(recipientName: String, threadId: Long) {
         maybeCreateChannel(name = context.getString(R.string.message_not_sent_short))
 
-        val notificationId = threadId.hashCode()
+        val notificationId = generateRandomId().hashCode()
         val intent = Intent(context, ThreadActivity::class.java).apply {
             putExtra(THREAD_ID, threadId)
         }