Enforce ISerializable for data types

[longfin]

When an object is serialized in .NET, it is often necessary for that field to be serializable. (e.g., best practices about custom exceptions), And when the object being serialized is out of our control, this can be a big problem.

So rather, I suggest that we proactively implement ISerialzable for the types we expect to be treated as data in Libplanet, and prevent this implicit field serialization. This can be easily applied to types for which we already have (de)serialzation methods, such as Block<T> or Transaction<T>.

The following is an example when applied to Transaction<T>.

 public sealed class Transaction<T> : IEquatable<Transaction<T>>, ITxExcerpt, ISerializable
        where T : IAction, new()
{
        protected Transaction<T>(SerializationInfo info, StreamingContext context)
            : this(new Bencodex.Codec().Decode(info?.GetValue<byte[]>("asBencodex")))
        {
        }

        public void GetObjectData(SerializationInfo info, StreamingContext context)
        {
            info.AddValue("asBencodex", new Bencodex.Codec().Encode(ToBencodex()));
        }
}

[dahlia]

It would be great if we can enforce it using static analysis (lint). I have no idea if there are any lints having such rule though…

[greymistcube]

I wish it was that simple, but I think we might want to also enforce something like IBencodexSerializable interface for data types (although this is for a slightly different reason; hence me "pre-emptively" working on #2457). In any case, byte array serialization and Bencodex serialization is left freely up to each class at the moment. This has became an issue while working on PBFT as PBFT will tack on many more data types to existing one, and there is no real standard to follow. 🙄

If we have a strong enough contract, then I think it'd help for outside/new contributors to follow more easily. 😗

[longfin]

On the other hand, this effort may be unnecessary or will affect only a very limited duration since .NET seems to decide to step down the legacy serialization API, including ISerializable. (see also)