Auth is ignored in the second call to the client

[stepancheg]

trafficstars

This is what I'm trying to do:

        let client = oci_client::Client::new(ClientConfig::default());
        eprintln!("Trying to list with anonymous auth...");
        let mut tags = client
            .list_tags(&image, &RegistryAuth::Anonymous, None, None)
            .await;
        if let Err(
            OciDistributionError::UnauthorizedError { .. }
            | OciDistributionError::AuthenticationFailure(_),
        ) = tags
        {
            eprintln!("Trying to list with docker auth...");
            let auth = fetch_docker_auth(&image).await?;
            tags = client.list_tags(&image, &auth, None, None).await;
        }

Second call fails because auth parameter is ignored.

https://github.com/oras-project/rust-oci-client/blob/a1a959791d18815c6422053c79b1e5e869c8aa78/src/client.rs#L437-L438

https://github.com/oras-project/rust-oci-client/blob/a1a959791d18815c6422053c79b1e5e869c8aa78/src/client.rs#L399-L403

The logic seems incorrect: we should either store auth or pass in parameters, but not both. And generally function parameters should not be ignored.