feat(esp_http_server): Make HTTP(S)_SERVER_EVENT events optional

Make it possible to disable http(s) server events. This improves
performance of the server, as http server creates events on every signle
read or write to the socket.

components/esp_http_server/include/esp_http_server.h

@@ -23,8 +23,6 @@ extern "C" {
 
 #define ESP_HTTPD_DEF_CTRL_PORT         (32768)    /*!< HTTP Server control socket port*/
 
-ESP_EVENT_DECLARE_BASE(ESP_HTTP_SERVER_EVENT);
-
 /**
  * @brief   HTTP Server events id
  */
@@ -40,11 +38,15 @@ typedef enum {
     HTTP_SERVER_EVENT_STOP,            /*!< This event occurs when HTTP Server is stopped */
 } esp_http_server_event_id_t;
 
+#if CONFIG_HTTPD_ENABLE_EVENTS || __DOXYGEN_
+ESP_EVENT_DECLARE_BASE(ESP_HTTP_SERVER_EVENT);
+
 /** Argument structure for HTTP_SERVER_EVENT_ON_DATA and HTTP_SERVER_EVENT_SENT_DATA event */
 typedef struct {
     int fd;         /*!< Session socket file descriptor */
     int data_len;   /*!< Data length */
 } esp_http_server_event_data;
+#endif // CONFIG_HTTPD_ENABLE_EVENTS || __DOXYGEN_
 
 /*
 note: esp_https_server.h includes a customized copy of this