Port to Humble - Githubissues

This pull request ports the Darknet ROS to ROS 2 Humble adding several improvements, namely:

Elimination of the Darknet vendor due to the two pull-requests that got approved on Darknet directly https://github.com/AlexeyAB/darknet/pull/8782 and https://github.com/AlexeyAB/darknet/pull/8783
Porting of the changes in the vision_msgs, see also https://github.com/ros2/openrobotics_darknet_ros/issues/9
Automatic download of Yolo configuration files for Yolo V3, V4, V7 and their tiny variants when building with DOWNLOAD_YOLO_CONFIG=ON and a corresponding launch file that allows to switch easily between them.

ros2 / openrobotics_darknet_ros