Fix S1144 FP/FN: Do not raise on serializable members

[Tim-Pohlmann]

S1144 should not be raised for serializable members. This is useful if you cannot change the deserialization process but only need access to a subset of the members. Also, the exception needs to be added to RSPEC. Originally reported in #8504

        [Serializable]
        public class ConfigOptionDto
        {
            private string type;  // FP
            private string key { get; set; }  // FP
            [NonSerialized]
            private string value;  // FN
        }