Reconnect event callback is shared with much more often events

To get notified about reconnect event, the CLIENT_EVENT_TYPE event type of MARIADB_OPT_STATUS_CALLBACK is being used in current implementation. This makes it shared with status change event(and maybe others) that happens much more often and regularly. That makes too many redundant calls if application is interested in reconnect event only. Possibly using different callback or subscription for certain event types could be a better idea