Moved macro AUTO_CLEAR_CLOSED_SOCKET and CLEAR_CLOSED_SOCKET_INTERVAL from st_object_pool to st_server, which means st_client won't support this feature anymore, because closed sockets in st_client maybe are reconnecting to the server, we should not clear them.
Move asynchronous graceful close logic from st_tcp_socket to st_connector and st_server_socket.
Reserved timer 10 ~ 19 to st_server_socket and st_server.
Fix bug: graceful_close and force_close cannot reconnect to the server(introduced by asynchronous graceful close feature).