Update repository status page to support RPM

[cottsay]

This change involved deprecating the existing ubuntu-specific command line argument --os-code-name-and-arch-tuples in place of one which conveys the OS name as well.

I tried to make all of the changes backwards-compatible, and I'll make a follow-up change to remove the deprecated parts of the code:

• Drop add_argument_os_code_name_and_arch_tuples
• Drop build_debian_repos_status_page
• Make build_repos_status_page.py hard-require the new argument format

I also needed to modify _strip_os_code_name_suffix with a special case for RPM, since the code name is just a number. I combined the short OS name with the code name, yielding something like fc31 or el7, which is the release suffix the RPMs will have. As it turns out, this is exactly the right place to strip to make the ROS package versions line up correctly. Non-ROS packages look OK as well.

[cottsay]

Example output: http://54.165.81.143/status_page/eloquent_centos.html

I'll note that the way the configuration is structured, you can't mix-and-match package formats in the same group of repository URLs. They need to be separated like this:
https://github.com/ros2/ros_buildfarm_config/blob/4e5eb924ada69bbcb0150039b43ec94cfc8ca087/index.yaml#L51-L59

[cottsay]

This change has been deployed to build.ros.org and build.ros2.org.