pov: Consider making tests insensitive to child ordering about haskell

[kytrinyx]

Yeah, allowing either ordering would be great.

[petertseng]

Surveying the other languages that implement this exercise.

• xgo allows any ordering because it only checks for the presence of edges, and sorts the edges before checking presence.
• xclojure seems to also be sensitive to ordering; IIRC clojure vectors (denoted by []) only compare equal if the elements are in the same order. Though I will note that Clojure, in expecting the former parent comes after the former children in a vector, expresses an ordering that is more likely to be the default choice, since conj onto a vector appends onto the end of the vector [1]. Nevertheless, it could be worth filing an issue for them as well.

[1]: Note that this is the opposite situation as a Clojure list or a Haskell list, both of which conj/cons/(:) onto the front.

[petertseng]

Expanding more on the work required for this track:

This matters when we are reparenting a node that has both a parent and some children. That means the "reparenting kids" and "reparenting cousins" test cases.