Added ros_buildfarm_config to be used in the Gazebo buildfarm

[j-rivero]

The PR adds the ros_buildfarm_config to be used with ros_buildfarm code to generate jobs in the build.o.o Jenkins. The configuration can generate four jobs of two categories:

• colcon_any-manual: jobs designed to be triggered manually and can consume any VCS file (harmonic is set as an example). Run on plain docker nodes (no GPU).
  • ci__colcon_any-manual_ubuntu_jammy_amd64
  • ci__colcon_any-manual_ubuntu_noble_amd64
• colcon_gpu_any-manual: idem than before but runs on nvidia nodes.
  • ci__colcon_gpu_any-manual_ubuntu_jammy_amd64
  • ci__colcon_gpu_any-manual_ubuntu_noble_amd64

I added a README.md file with the rationale of this ros_buildfarm_config and the way of generating the jobs.

The ros_buildfarm code requires ros-infrastructure/ros_buildfarm#1059 to make the GPU jobs to work and the Jammy builds depend on ros-infrastructure/ros_buildfarm#1062

[cottsay]

I don't have 100% of the context needed on the Gazebo side of things, but I don't see any problems here.

It might be good to figure out how to handle the python3-distutils key at some point. If it needs to be skipped here, then it probably needs to be skipped for end users as well, which isn't great. Not a problem that we need to solve here.