Bump to 247.3-2 for systemd-oomd finishes and systemd-oomd-defaults subpackage
    
    Changes for https://fedoraproject.org/wiki/Changes/EnableSystemdOomd.
    Backports primarily PR #18361, #18444, and #18401 (#18401 is not merged
    at the time of writing this commit) + some minor PRs to handle conflicts.
    Creates systemd-oomd-defaults subpackage to install unit drop-ins that
    will configure systemd-oomd to monitor and act.