Add support for msgpack-based serialization of GufeTokenizables

[dotsdl]

Currently, we use JSON-based encoding as our general approach for serializing representations of GufeTokenizables, either in their dict, keyed_dict, or keyed_chain forms. However, JSON has several known disadvantages, including being relatively slow to parse for large objects and being space-inefficient for numeric datatypes. These limitations have bitten us in particular for ProtocolDAGResult objects, which often feature numerical data as key results.

To address this, we should pursue msgpack as an alternative serialization mechanism in addition to JSON. This could over time overtake JSON as our default approach for serialization in automated systems, while still retaining JSON as an option for cases in which human-readability is more valuable, or where a string representation of a full GufeTokenizable is required.