Fixes robot model issues on Noetic (visual links are no longer considered as collision links if the latter aren't defined)
Removes definition of TEST_COUT using googletest internal namespaces: There are different versions of googletest on the various target OS for the ROS versions leading to issues particularly on Noetic. The previous ROS-version-dependent fix did not work on Buster. By replacing this with a minimal shared header we both reduce duplication and fix the build issues on Debian buster.