In test envs shut down tracker immediately after finishing the test

[josecelano]

In some tests, we run the tracker, for example:

        #[tokio::test]
        async fn should_fail_when_the_uploaded_param_is_invalid() {
            INIT.call_once(|| {
                tracing_stderr_init(LevelFilter::ERROR);
            });

            let env = Started::new(&configuration::ephemeral().into()).await;

            let mut params = QueryBuilder::default().query().params();

            let invalid_values = ["-1", "1.1", "a"];

            for invalid_value in invalid_values {
                params.set("uploaded", invalid_value);

                let response = Client::new(*env.bind_address()).get(&format!("announce?{params}")).await;

                assert_bad_announce_request_error_response(response, "invalid param value").await;
            }

            env.stop().await;
        }

When we stop the env (env.stop().await) we should shut it down immediately. It does not make sense to wait 90 seconds for tests.

#[instrument(skip(handle, rx_halt, message))]
pub async fn graceful_shutdown(handle: axum_server::Handle, rx_halt: tokio::sync::oneshot::Receiver<Halted>, message: String) {
    shutdown_signal_with_message(rx_halt, message).await;

    tracing::debug!("Sending graceful shutdown signal");
    handle.graceful_shutdown(Some(Duration::from_secs(90)));

    println!("!! shuting down in 90 seconds !!");

    loop {
        sleep(Duration::from_secs(1)).await;

        tracing::info!("remaining alive connections: {}", handle.connection_count());
    }
}

cc @da2ce7