Implement `Clone` and `Debug` for `Dsu`

[NotLeonian]

Implement the Clone and Debug traits for Dsu.

The Clone trait can be derived.
For the Debug trait, discussion is needed regarding the output format.
I think deriving it is acceptable since the groups function allows checking connected components.

[NotLeonian]

Unless there are any other opinions on the output format, I plan to submit a PR with this implementation starting tomorrow.
If you have any concerns or suggestions, I would appreciate it if you could let me know.