Enable parameterless deserialization

[shustinm]

Is your feature request related to a problem? Please describe. Calling __init__ creates API constraints on the user.

Describe the solution you'd like Call cls.__new__ directly in the from_bytes implementation, similarly to pickle. I feel like this is the most natural solution to this problem given the nature of the library.

Describe alternatives you've considered Currently, StructMeta overrides the from_bytes and from_stream methods with ones that have injected arguments, meaning that there's still API for deserializing non default-constructable structs. The issue with this method is that deserializing into a struct still requires initializing one with fake arguments. Another solution is to either force or recommend users to implement their own classmethods for creating objects instead of custom constructors.