Modernize codebase

[TorstenSchmitz]

1. fix clippy lints
   - adds <'_> where clippy warned about inconsistently elided lifetimes, noise.
2. update to rust edition 2024
   - adds use crate:: in a few places
   - impl Display instead of error::error::description
   - add a few missing unsafe blocks
   - AtomicBool::new()
3. store errno in GeneralError and get explanation for it with strerror_r.
4. also an .editorconfig and empty .rustfmt.toml that can't hurt, my editor was picking up a config from a somewhere else at first