`garden-ai purge` to get rid of any local Docker artifacts created/pulled by Garden

[WillEngler]

Because Garden goes and runs Docker commands on behalf of the user, they will end up with cruft images eventually. There should be a command that removes any Docker images and containers created or pulled by Garden. That way the user doesn't have to fumble around with docker commands to reclaim disk space.

garden-ai weed might be fun too 🤔

Assumptions:

1. 2.

Acceptance Criteria

Given..., when..., then...

[ascourtas]

may need to rethink component