FileIO should store a concrete storage config rather than raw hashmap.

### Is your feature request related to a problem or challenge?

The storage configs may contain sensitive data like credentials, storing them in a raw hashmap makes some operatiions like Debug, Display, Serialization unsafe and leaking them.

### Describe the solution you'd like

We should store a concrete stroage config struct in `FileIO`, and mark each sensitive values in them.

### Willingness to contribute

I can contribute to this feature independently