Add optional `msgspec <https://jcristharif.com/msgspec/>`_ support over
TCP streams as an alernative, faster MessagePack codec.

This get's us moving toward typed messaging/IPC protocols. Further,
``msgspec`` structs may be a valid tool to start for formalizing our "SC
dialog un-protocol" messages as described in `#36
<https://github.com/goodboy/tractor/issues/36>`_`.