[Navigation Refactoring] Cleaning up structures

TODOs

• Implement laser_obstacle_node which accumulates the last n laser range readings to an nav_msgs/OccupancyGrid for laser obstacle input in planning_node
  • Currently done in follow_path_node for direct obstacle avoidance there
• Implement follow_path_node containing all steering commands calculated and sent
• path_planning_node needs to monitor current deviation of /pose from path
  • Recalculate path if too far off
• Recalculate path if obstacle appears on (or near) path
• Add state machines and state transitions in planning_node and others
• Smoothly increase speeds in contrast to current speeds
  • Initial and final ramping
• Slow down when path curvature is too high in partial path before robot

Debug

• Change goal topic back to /planning_node/target_pose

Misc

• Also merge https://gitlab.uni-koblenz.de/robbie/homer_bringup/-/merge_requests/33