Allow relabeling and changing layout when calling to_undirected

[knutwalker]

• to_undirected in the Rust API accepts an optional layout, which is not exposed in the Python API
• Additionally, allow relabelling in the same step
• Maybe we can extend the Layout enum to smth like { Unsorted, SortedById, SortedByDegree, DeduplicatedById, DeduplicatedByDegree } ?