A crate providing macros for creating spans in various detail levels. coarse! should be used for top-level operations, whereas
detail! should be used in plumbing crates unless their operations are likely to cost a lot of time.
The application is supposed to explicitly turn on tracing via gix-features.
Crates that use gix-features should use gix_features::trace, and those who don't can use gix_trace directly.