Add a new toddler to update PDC when packages get retired
This is a port of the RetireComponentHandler handler of pdc-updater
This toddler accepts two message topics:
- org.fedoraproject.*.git.receive which runs on this specific
repository when a ``dead.package`` file is added to it.
- org.fedoraproject.*.toddlers.trigger.pdc_retired_packages which
runs over all the repositories and all branches to syncs entirely
PDC and koji.
Signed-off-by: Pierre-Yves Chibon <firstname.lastname@example.org>