Add provisioning state tracking and LED indication

See the "provisioning state" README section for documentation.

With this change we also reshuffle board led confguration somewhat:
where possible, secondary LED is used for provisioning. Where only one
is available (ESP8266), it is shared with LED1.

demo-c is modified to not blink the LED on its own and only turn it on during init.
This way app code doesnt interfere with provisioning library too much and the app behaves sensibly on ESP8266.

CL: Add provisioning state tracking and LED indication

PUBLISHED_FROM=a29b1c6e4a7d3362b18aab26bfbe1c639001625f

src/main.c

@@ -4,11 +4,13 @@
 #include "mgos_wifi.h"
 #endif
 
-static void led_timer_cb(void *arg) {
-  bool val = mgos_gpio_toggle(mgos_sys_config_get_board_led1_pin());
-  LOG(LL_INFO, ("%s uptime: %.2lf, RAM: %lu, %lu free", val ? "Tick" : "Tock",
-                mgos_uptime(), (unsigned long) mgos_get_heap_size(),
-                (unsigned long) mgos_get_free_heap_size()));
+static void timer_cb(void *arg) {
+  static bool s_tick_tock = false;
+  LOG(LL_INFO,
+      ("%s uptime: %.2lf, RAM: %lu, %lu free", (s_tick_tock ? "Tick" : "Tock"),
+       mgos_uptime(), (unsigned long) mgos_get_heap_size(),
+       (unsigned long) mgos_get_free_heap_size()));
+  s_tick_tock = !s_tick_tock;
   (void) arg;
 }
 
@@ -85,15 +87,16 @@ static void button_cb(int pin, void *arg) {
 
 enum mgos_app_init_result mgos_app_init(void) {
   char buf[8];
-  /* Blink built-in LED every second */
+
   int led_pin = mgos_sys_config_get_board_led1_pin();
   if (led_pin >= 0) {
     LOG(LL_INFO, ("LED pin %s", mgos_gpio_str(led_pin, buf)));
-    mgos_gpio_set_mode(led_pin, MGOS_GPIO_MODE_OUTPUT);
-    mgos_set_timer(1000, MGOS_TIMER_REPEAT, led_timer_cb, NULL);
+    mgos_gpio_setup_output(led_pin,
+                           mgos_sys_config_get_board_led1_active_high());
   }
-  mgos_gpio_set_mode(led_pin, MGOS_GPIO_MODE_OUTPUT);
-  mgos_gpio_write(led_pin, !mgos_sys_config_get_board_led1_active_high());
+
+  /* Simple repeating timer */
+  mgos_set_timer(1000, MGOS_TIMER_REPEAT, timer_cb, NULL);
 
   /* Publish to MQTT on button press */
   int btn_pin = mgos_sys_config_get_board_btn1_pin();