Change default serialization format for serialize/deserialize methods to binary

[stinodego]

Our serialization methods currently all work with JSON strings. This is useful as it's human readable and certain protocols will require JSON structures, but we should also have a more optimized binary serialization format.

bincode seems like a good candidate, since it's already in our dependencies.

The intended API would be to add a format parameter to (de)serialization methods with the options "json" and "bincode". Other useful formats could potentially be added in the future.

[ritchie46]

All for this. Though I do think we should mark the other formats as unstable.

[stinodego]

Update: we will use the ciborium crate for binary serialization:
https://crates.io/crates/ciborium

The associated format will be named "binary". And this will become the default format.