[serde] Implement is_human_readable on (de)serializer

[theli-ua]

is_human_readable by default is implemented as returning true Ion's (de)serializer should return false for binary encodings. This is used by serialize/deserialize to use different encoding in serde (and/or custom serialize/deserialize implementations). One such example would be std::net::IpAddr which uses string representation in human readable version and byte arrays otherwise.

[theli-ua]

https://docs.rs/serde/latest/serde/trait.Serializer.html#method.is_human_readable

[theli-ua]

Something like this should pass once this is implemented

    #[test]
    fn human_readable() {
        // IpAddr has different repr based on if codec is considered
        // human readable or not {true: string, false: byte array}
        let ip: IpAddr = "127.0.0.1".parse().unwrap();
        let expected_binary = [
            224, 1, 0, 234, 235, 129, 131, 216, 134, 113, 3, 135, 179, 130, 86, 52, 233, 129, 138,
            182, 33, 127, 32, 32, 33, 1,
        ];
        let expected_s = "\"127.0.0.1\" ";
        let binary = to_binary(&ip).unwrap();
        assert_eq!(&binary[..], &expected_binary[..]);
        let s = to_string(&ip).unwrap();
        assert_eq!(s, expected_s);
        assert_eq!(&from_ion::<IpAddr, _>(binary).unwrap(), &ip);
        assert_eq!(&from_ion::<IpAddr, _>(s).unwrap(), &ip);
    }

[desaikd]

Thank you for reporting this issue @theli-ua! I was able to reproduce the issue with your provided sample test. I will investigate more on the issue and also look at your reference on is_human_readable.