`build_ic_set` on IC distributions with continuous functions fails

```python
ic_gen = ex.ic.RandomSineWaves1d(1)
ex.build_ic_set(ic_gen, num_points=100, num_samples=10, key=jax.random.PRNGKey(0))
```

since `RandomSineWaves1d` builds the discretized IC state via first building the continuous function and then discretizing it on the grid which is different from `RandomTruncatedFourierSeries`.