Consider excluding `options` from `CodeModel.get_model_state()`

In the `CodeModel` class:

```python
def get_model_state(self) -> dict:
return {
"options": self.options,
"code": self.selected,
"nodes": self.num_nodes,
"cpus": self.num_cpus,
"ntasks_per_node": self.ntasks_per_node,
"cpus_per_task": self.cpus_per_task,
"max_wallclock_seconds": self.max_wallclock_seconds,
}
```

I added the `options` field (in #946) surely for some reason, but it doesn't make much sense to me now. This issue is a reminder to revisit the code and see if the field is actually needed, and if possible (strongly suggested), remove it.