Keep around retrigger artifacts for a shorter period of time

We need the robust bot runs, but those trigger around 15 pipelines which by itself, generates around 75G of artifacts for a single bot run. That said, we don't need to keep bot artifacts around for long as they are used for testing our changes and they get in pretty fast.

AC: Implement a way to identify artifacts belonging to retriggers, and remove them from the storage after 1-2 weeks