mission_block: change loiter handling logic

- add ability of "heading wait" for NAV_CMD_LOITER_TIME_LIMIT
- For both LOITER_TIME and LOITER_TO_ALT in fixed-wing flight, unify logic:
--> reach position --> start loitering --> reach altitude --> start timer (if applicable)
	--> reach exit heading (if applicable) --> declare mission item reached

Signed-off-by: Silvan Fuhrer <silvan@auterion.com>

src/modules/mavlink/mavlink_mission.cpp

@@ -1640,6 +1640,7 @@ MavlinkMissionManager::format_mavlink_mission_item(const struct mission_item_s *
 
 		case NAV_CMD_LOITER_TIME_LIMIT:
 			mavlink_mission_item->param1 = mission_item->time_inside;
+			mavlink_mission_item->param2 = mission_item->force_heading;
 			mavlink_mission_item->param3 = mission_item->loiter_radius;
 			mavlink_mission_item->param4 = mission_item->loiter_exit_xtrack;
 			break;