Ship systemd-oomd-defaults, drop earlyoom
`systemd-oomd-defaults` pulls in `systemd-oomd` and provides a default
configuration and preset.
Also remove `earlyoom` that is previously part of `comps` for
Workstation and KDE.
See https://fedoraproject.org/wiki/Changes/EnableSystemdOomd
Signed-off-by: Michel Alexandre Salim <salimma@fedoraproject.org>