Let tries carry a payload

[dennis-tra]

When implementing the trie routing table in go-kademlia we found it would be useful if the trie data structure carried some data in each of its leaves.

This PR adds a generic Data property to the trie.

Caveats

• This breaks the public API
• We could keep the New method without type parameters that calls another NewWithData[T any] constructor, which sets the data type to any. This way downstream projects that use the New probably won't notice
• The behavior of unions and intersections would need to be defined and documented in a code comment.