Add missing exec dependencies

[Ryanf55]

This allows --packages-up-to to be used correctly be declaring depenedencies. Also, it supports rosdep adding dependencies when we get to releasing binaries.

Tested with rosdep, no new errors introduced:

ryan@B650-970:~/Dev/ardu_ws$ rosdep install --from-paths src --ignore-src 
ERROR: the following packages/stacks could not have their rosdep keys resolved
to system dependencies:
ros_gz_bridge: Cannot locate rosdep definition for [gz-transport12]
ardupilot_gazebo: Cannot locate rosdep definition for [libgz-sim7-dev]
ros_gz_sim: Cannot locate rosdep definition for [gz-math7]
ros_gz_image: Cannot locate rosdep definition for [gz-transport12]
sdformat_urdf: Cannot locate rosdep definition for [sdformat13]

Now, it builds the packages you need for bringup.

ryan@B650-970:~/Dev/ardu_ws$ colcon build --packages-up-to ardupilot_gz_bringup
Starting >>> ardupilot_gz_description
Starting >>> ardupilot_gz_gazebo
Starting >>> ardupilot_sitl
Starting >>> ros_gz_sim
Finished <<< ardupilot_gz_description [0.07s]
Finished <<< ardupilot_gz_gazebo [0.08s]
Finished <<< ros_gz_sim [0.10s]                                                            
Finished <<< ardupilot_sitl [1.95s]                
Starting >>> ardupilot_gz_bringup
Finished <<< ardupilot_gz_bringup [0.15s]                  

Summary: 5 packages finished [2.34s]