The new rbinstall.distro_info module contains definitions for all the

Linux distributions that are supported by the installer. This defines

the packages and other commands needed to install Review Board and its

dependencies across various versions of Amazon Linux, Arch Linux,

CentOS, Debian, Fedora, openSUSE, RHEL, Rocky Linux, RHEL, and Ubuntu.
The definitions are parsed by functions in rbinstall.install_steps,

which turns them into commands to be run for handling package

installation.
Unit tests exist for all supported distros, in order to help catch any

changes to package installation. These have also all been tested against

Docker-based installs of each distro.

Unit tests pass.
Tested these definitions on all supported Linux distributions.