esp32/modnetwork: Implement dhcp_hostname for WLAN.config().

ports/esp32/modnetwork.c

@@ -445,6 +445,11 @@ STATIC mp_obj_t esp_config(size_t n_args, const mp_obj_t *args, mp_map_t *kwargs
                         cfg.ap.channel = mp_obj_get_int(kwargs->table[i].value);
                         break;
                     }
+                    case QS(MP_QSTR_dhcp_hostname): {
+                        const char *s = mp_obj_str_get_str(kwargs->table[i].value);
+                        ESP_EXCEPTIONS(tcpip_adapter_set_hostname(self->if_id, s));
+                        break;
+                    }
                     default:
                         goto unknown;
                 }
@@ -494,6 +499,12 @@ STATIC mp_obj_t esp_config(size_t n_args, const mp_obj_t *args, mp_map_t *kwargs
             req_if = WIFI_IF_AP;
             val = MP_OBJ_NEW_SMALL_INT(cfg.ap.channel);
             break;
+        case QS(MP_QSTR_dhcp_hostname): {
+            const char *s;
+            ESP_EXCEPTIONS(tcpip_adapter_get_hostname(self->if_id, &s));
+            val = mp_obj_new_str(s, strlen(s));
+            break;
+        }
         default:
             goto unknown;
     }