RainMaker library: Minor changes (#5092)

- Use Serial.print instead of log_i for QR code helper information,
  so that it is always printed by default.
- Expose the RainMaker factory reset and wifi reset APIs.
- Simplify example to have only a Switch device. Create another example for custom device.
- Enable push button based Factory reset and Wi-Fi reset.
- Added support for the TimeZone service.
- Moved API doc to RainMaker library's top level README.
- Other minor doc changes.

libraries/RainMaker/src/RMakerUtils.h

@@ -0,0 +1,16 @@
+#include "esp_system.h"
+#if ESP_IDF_VERSION_MAJOR >= 4 && CONFIG_IDF_TARGET_ESP32
+
+#include <esp_rmaker_utils.h>
+
+static void RMakerFactoryReset(int seconds)
+{
+    esp_rmaker_factory_reset(seconds);
+}
+
+static void RMakerWiFiReset(int seconds)
+{
+    esp_rmaker_wifi_reset(seconds);
+}
+
+#endif