esp32: Fix not the right time spent in a deep sleep

Before entering the deep sleep, the RTC and FRC counters are synchronized. Updating the boot_time.
Added a unit test for this case.
Fixed warnings for MULTIPLE_STAGES

Closes https://github.com/espressif/esp-idf/issues/1840

components/newlib/platform_include/esp_newlib.h

@@ -38,4 +38,9 @@ void esp_setup_syscall_table();
  */
 void esp_set_time_from_rtc();
 
+/*
+ * Sync counters RTC and FRC. Update boot_time.
+ */
+void esp_sync_counters_rtc_and_frc();
+
 #endif //__ESP_NEWLIB_H__