Dill pickling chex.dataclass blows the stack

Chex dataclasses can be pickled with `pickle`, but not with `dill`:

```python
import dill
import pickle

import chex

@chex.dataclass
class Point:
x: float
y: float

# Works fine.
pickle.dumps(Point(x=1.0, y=2.0))

# Generates `RecursionError: maximum recursion depth exceeded`
dill.dumps(Point(x=1.0, y=2.0))
```