commander: write timestamp of commander_state topic on init and state change

src/modules/commander/commander.cpp

@@ -1267,6 +1267,7 @@ int commander_thread_main(int argc, char *argv[])
 	status_flags.rc_input_blocked = false;
 	status.rc_input_mode = vehicle_status_s::RC_IN_MODE_DEFAULT;
 	internal_state.main_state = commander_state_s::MAIN_STATE_MANUAL;
+	internal_state.timestamp = hrt_absolute_time();
 	main_state_prev = commander_state_s::MAIN_STATE_MAX;
 	status.nav_state = vehicle_status_s::NAVIGATION_STATE_MANUAL;
 	status.arming_state = vehicle_status_s::ARMING_STATE_INIT;

src/modules/commander/state_machine_helper.cpp

@@ -407,6 +407,7 @@ main_state_transition(struct vehicle_status_s *status, main_state_t new_main_sta
 		if (internal_state->main_state != new_main_state) {
 			main_state_prev = internal_state->main_state;
 			internal_state->main_state = new_main_state;
+			internal_state->timestamp = hrt_absolute_time();
 		} else {
 			ret = TRANSITION_NOT_CHANGED;
 		}