Investigate using serde in the bindings

[VivekPanyam]

Most of the code in language bindings just does type conversion. If you squint a bit, this fits into serde's definition of serialization/deserialization.

You could implement a serde::Serializer that "serializes" things into PyO3/Neon objects and a serde::Deserializer that does the opposite.

People have done this and implemented things like neon-serde and pythonize. This would significantly simplify boilerplate code in the language bindings, make things easier to maintain, and also make it easier to add support for new languages.