Dracut modules for xCAT Genesis

Subdirectories:

* `el/`     — EL (RHEL/Rocky/Alma) dracut module
* `ubuntu/` — Ubuntu dracut module (adapted library paths, dpkg instead of rpm)

Both modules share the same xcat-cmdline.sh, dhclient.conf, dhclient-script,
rsyslog.conf, and xcatroot files (copied, not symlinked, to avoid issues
when cp -a copies the module into the dracut modules directory).

Key differences in ubuntu/module-setup.sh vs el/module-setup.sh:
* Uses dpkg instead of rpm
* Uses /etc/os-release instead of /etc/redhat-release
* rsyslog modules from /usr/lib/<triplet>/rsyslog/ instead of /lib64/rsyslog/
* libnss_dns from /lib/<triplet>/ instead of /lib64/
* udev rules from /usr/lib/udev/rules.d/ instead of /lib/udev/rules.d/
* mkfs.btrfs instead of mkfs.xfs
* chrony config checked at both /etc/chrony.conf and /etc/chrony/chrony.conf
