Clean up `traffic_light_reg_elem`

[JStephenHuang]

• Remove any the mock function that handles the detection class id for traffic light reg elem and implement class_id to TrafficLightState method under traffic light reg elem class. (See for traffic sign implementation)

• Also clean up the hd_map, remove any irrelevant comments or unused functions.

For example:

• Remove this:
  

  wato_monorepo/src/world_modeling/hd_map/src/hd_map_router.cpp

  Lines 184 to 207 in b573a4f

  	// Mock function to get traffic light state (to change or remove)
  	TrafficLightState HDMapRouter::get_traffic_light_state(
  	const vision_msgs::msg::Detection3D::SharedPtr traffic_light_msg_ptr) {
  	if (traffic_light_msg_ptr->results.empty()) {
  	return TrafficLightState::Unknown;
  	}
  	TrafficLightState traffic_light_state = TrafficLightState::Unknown;
  	float base_score = 0;
  	for (const auto& result : traffic_light_msg_ptr->results) {
  	if (result.hypothesis.score > base_score) {
  	if (result.hypothesis.class_id == "GREEN") {
  	traffic_light_state = TrafficLightState::Green;
  	} else if (result.hypothesis.class_id == "YELLOW") {
  	traffic_light_state = TrafficLightState::Yellow;
  	} else if (result.hypothesis.class_id == "RED") {
  	traffic_light_state = TrafficLightState::Red;
  	}
  	base_score = result.hypothesis.score;
  	}
  	}
  	return TrafficLightState::Green;
  	}