Enable logs in tests

[MarcoIeni]

The logs are super useful. For example I was debugging #174 and by enabling logs I saw the following which is very useful:

It would be nice to enable logs for all tests by default.

I copy pasted the following to enable logs:

    tracing_subscriber::fmt()
        .with_env_filter(
            EnvFilter::builder()
                .with_default_directive(tracing::Level::INFO.into())
                .from_env()
                .expect("Cannot load RUST_LOG"),
        )
        .init();

What do you think?

[Kobzol]

We already depend on https://docs.rs/tracing-test/latest/tracing_test/. You can just slap #[traced_test] on top of a test to enable tracing log output in that test. I guess it would be nice to add this to the development documentation :)