RFC 629: Don't require log output in SSBC resolvers

Created by: eseliger

Currently, we parse the execution logs to compute some resolver values. We should stop doing that and treat that column as ephemeral, or high cost to fetch. That probably means normalizing some of the data we derive from the logs, and making sure that step logs are only loaded when they are actually rendered. As a side-effect it would be nice if larger data from that column like the git patch would be extracted and stored in minIO using the uploadstore package.