Replace `log_err()` by `#[tracing::instrument(err(Debug))]`

[ejpcmac]

Context

We currently log errors through an extension trait on Result<T, E> that adds a log_err method. This has two issues:

1. this is verbose and easy to forget,
2. the reported module in logs is the helpers module instead of the module where the error is generated.

Concept

Let’s enable err(Debug) wherever applicable and remove all .log_err() instances.

Note

If needed in some case, Result::inspect_err can be used as well.