Better (de)serializers

[Auties00]

• Allow constructors to be used as deserializers
• Make the methods in ProtobufInputStream/ProtobufOutputStream mixins so one can consume them in a deserialization/serialization flow
• Would be cool to maybe have the option of having the context of the owner object in the serializer, maybe something like a parameter annotated with @ProtobufSerializer.Caller/@ProtobufDeserializer.Caller
• two way paths for (de)serialization, this will be incredibly complex to implement and it's not that useful but I'd like to have it in

[Auties00]

• Add an option to use the builder in the spec instead for object building and return that instead of the built element so we can have non-protobuf mandatory immutable fields in the final obj