Automatically delete old GCP Artifact Registry Storage test images

[teor2345]

Motivation

They are costing us a bit, and it's increasing every month.

We want to keep them around long enough so that PRs that are still on the same commit can be re-run with the same image.

Designs

Delete test images from GCP Artifact Registry Storage after 3 weeks.
(Most PRs get updated every few days, and merge within 1-2 weeks.)

[mpguerra]

Hey team! Please add your planning poker estimate with Zenhub @arya2 @conradoplg @dconnolly @gustavovalverde @oxarbitrage @teor2345 @upbqdn

[gustavovalverde]

@mpguerra as I'm finishing this one. I'd prefer to have it in this sprint.