MM-33708 - Add MentionCountRoot column to ChannelMembers (#17099)

* added new column for root-only mentions

Co-authored-by: Mattermod <mattermod@users.noreply.github.com>

store/sqlstore/user_store.go

@@ -1634,6 +1634,7 @@ func (us SqlUserStore) GetUsersBatchForIndexing(startTime, endTime int64, limit
 				cm.LastViewedAt,
 				cm.MsgCount,
 				cm.MentionCount,
+				cm.MentionCountRoot,
 				cm.NotifyProps,
 				cm.LastUpdateAt,
 				cm.SchemeUser,