Implement a suite of classical functional data structures in Troupe

[aslanix]

We would like to extend the Troupe test suite (and potentially the standard library) with a set of classical data structures. This will be helpful for performance benchmarks. One source of the algorithms describing such data structures is https://www.amazon.com/Purely-Functional-Data-Structures-Okasaki/dp/0521663504 (see also Okasaki's thesis at https://www.cs.cmu.edu/~rwh/students/okasaki.pdf) Down the road, one can examine extensions of these data structures with information flow, i.e., to support heterogeneity in labels.