Add ID command support

[bczhc]

This adds a method to send ID command to the server.

Take #296 as an example. Netease 126 email requires id command call before any further commands (though it's a very nonstandard way and no spec enforces this). After this PR, it allows to do so to do a success 126 IMAP login.

fn main() -> anyhow::Result<()> {
    let password = "*";

    let domain = "imap.126.com";
    let client = imap::ClientBuilder::new(domain, 993).connect().unwrap();

    let mut imap_session = client.login("bczhc0@126.com", password).map_err(|e| e.0)?;

    let params = [
        ("version", Some("1.0.0")),
        ("vendor", None),
        ("name", None),
    ];

    let _id_response = imap_session.id(&params)?;
    imap_session.examine("INBOX")?;

    imap_session.logout()?;
    Ok(())
}

Fixes #151.

• https://datatracker.ietf.org/doc/html/rfc2971

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This change is