QoL: Make dataclass outputs easier to **

[liamhuber]

The standard dataclasses module lets you do this to a dataclass, my_dc, like **asdict(my_dc). See if we can get a sensible extension so it can be done in tab-completable way, e.g. **my_dc.asdict(). @JNmpi previously accomplished this on his branch by subclassing Dataclass directly.