fix<lint>: apply pedantic & non_exhaustive

[Mathieu-Lala]

Context

Addressing https://github.com/dequbed/rsasl/issues/14

I also added the clippy::pedantic warnings.

I believe most of the changes are useful, but we might want to do some cherry pick.

Summary of changes

Added

• add #[warn(clippy::{all,pedantic,exhaustive_enums,exhaustive_structs})] in lib.rs
• set #[allow(...)] for too verbose warnings in lib.rs (but they should be addressed)

Changed

• fix the warnings when possible
• use #[allow(...)] when the fix would produce side-effect (break api)

[Mathieu-Lala]

There is few #[allow(...)] we should fix before merging