Add support for RHEL 9 and compatible clones
I've already the detection code for RHEL 9 and clones in my local git repo, however, RHEL 9 suffers from the very same problem as Ubuntu 22.04 that the shipped PHP and MariaDB versions are too new for current ISPConfig codebase.
Also there are still some critical 3rd-party packages missing as of today, like rspamd, awstats, or pure-ftpd among a few more.