Enforce `event_id` being read as `np.ndarray` and `event_name` as `list` in Hazard readers.

Related to #910

In addition to checking that elements of `event_name` are strings when reading/writing, @chahank suggested to enforce the type for the container for both `event_name` and `event_id` (As the former expects a `list` and the latter an `ndarray`. 

As it is closely related to the checks added to address #910, we should also cover this issue.

See related PR for more details.