Add Iris model with a depth camera and downward-facing lidar#999

DanMesh wants to merge 1 commit intoPX4:mainPX4/PX4-SITL_gazebo-classic:mainfrom

DanMesh:iris-depth-camera-with-lidarDanMesh/PX4-SITL_gazebo:iris-depth-camera-with-lidarCopy head branch name to clipboard