Update IDF to e931fe9 and add esp-face (#2291)

* Update IDF to e931fe9 and add esp-face

* Fix PIO builds fail because of sketch size

* Fix example build failing for Arduino

tools/sdk/include/lwip/lwip/api.h

@@ -233,15 +233,6 @@ struct netconn {
       by the application thread */
   sys_mbox_t acceptmbox;
 #endif /* LWIP_TCP */
-
-#if ESP_THREAD_SAFE
-  /** point to the same mbox as recvmbox */
-  sys_mbox_t recvmbox_ref;
-#if LWIP_TCP
-  /** point to the same mbox as acceptmbox */
-  sys_mbox_t acceptmbox_ref;
-#endif
-#endif
   /** only used for socket layer */
 #if LWIP_SOCKET
   int socket;