Fixes T4952. Several issues:
- You review configuration values with arc set-config --show. This makes no sense and never has, I think it just predated arc get-config or was easier or something.
- Instead, review values with arc get-config and review details with arc get-config --verbose.
- Show better and more detailed information about all config sources.
- Establish and show default values from a new "default" source.
- With --trace include more information about attempts to read configuration files.
