structured-logging

Suggested on Telegram.

It may be easier to understand the examples if they don't show both distage and BIO at the same time, so we may want to have a variant of distage-example that uses just distage alone, using a monomorphic effect type everywhere.

Stumpless uses a scheme involving #definenames and macro functions to separate its portability measures from the application logic itself. This was originally done via a single header, include/private/config/wrapper.h, but as the library grows this single header has become bloated. Now features are instead contained in their own dedicated wrapper headers. Older features need to be moved to the