Change preferred_formatting_style default implementation to pass through FormattingFunction. #111
Description
Current behavior has the preferred formatting style functions of ContextHandler and AttachmentHandler return Default::default() which includes FormattingFunction::Display as the default, ignoring the formatting function requested when formatting the report.
This violates principle of least surprise. The counter-argument is that Debug handler is useful for operational security, (behavior which #106 changes)
Operational security should probably be documented in doc comments and in the upcoming book, rather than be included by default to surprising results. The design philosophy of Rootcause being easy to adopt as a replacement for e.g. Anyhow, should trump opsec considerations — all languages have opsec issues surrounding error handling, and ordinary techniques will suffice with rootcause.