This moves toward using https://pkg.go.dev/log/slog, which provides structured logging, levels, groups, and more formatting options, and https://github.com/chainguard-dev/clog for context-aware (s)logging.

This moves --log-policy to a root flag, and removes --debug and --quiet in favor of a --log-level flag.

The output should be identical to the previous logging output, with even more care taken to attribute arch-specific logs using slogctx.