Implement triangle count

**Description**
The Triangle Count algorithm counts the number of triangles for each node in the graph. A triangle is a set of three nodes where each node has a relationship to the other two. In graph theory terminology, this is sometimes referred to as a 3-clique. The Triangle Count algorithm in the GDS library only finds triangles in undirected graphs.

**Pointers**
[The clustering coefficient ](https://github.com/fslaborg/Graphoscope/blob/1d6f5b9b2336d804faab682c76207fda70672d14/src/Graphoscope/Measures/ClusteringCoefficient.fs#L15)makes use of triangles, which might give some ideas about the implementation.

**References**
https://neo4j.com/docs/graph-data-science/current/algorithms/triangle-count/