fix: MQTT tick not starting on connect and switch to esp_timer

- Tick should be updated on connect
- Dependency of system timer removed to avoid issues when updating via
  SNTP

Closes https://github.com/espressif/esp-mqtt/issues/225

lib/platform_esp32_idf.c

@@ -3,8 +3,8 @@
 #ifdef ESP_PLATFORM
 #include "esp_log.h"
 #include "esp_mac.h"
+#include "esp_timer.h"
 #include "esp_random.h"
-#include <sys/time.h>
 #include <stdlib.h>
 #include <stdint.h>
 
@@ -27,18 +27,9 @@ int platform_random(int max)
     return esp_random() % max;
 }
 
-int64_t platform_tick_get_ms(void)
+uint64_t platform_tick_get_ms(void)
 {
-    struct timeval te;
-    gettimeofday(&te, NULL); // get current time
-    long long milliseconds = te.tv_sec * 1000LL + te.tv_usec / 1000; // calculate milliseconds
-    // printf("milliseconds: %lld\n", milliseconds);
-    return milliseconds;
+    return esp_timer_get_time()/(int64_t)1000;
 }
 
-void ms_to_timeval(int timeout_ms, struct timeval *tv)
-{
-    tv->tv_sec = timeout_ms / 1000;
-    tv->tv_usec = (timeout_ms - (tv->tv_sec * 1000)) * 1000;
-}
 #endif