DM-32743: Add a container which can sync the latest schema into a registry

[spenczar]

This adds:

• A new executable script which takes the latest schema in the repo and submits it to a schema registry
• A Dockerfile which installs alert_packet and its dependencies, so that script can be run as Kubernetes Job
• Github Actions configuration to build the container and push it

The GH action won't work right now because appropriate secrets have not been loaded into this repo. Creds are added, yay