Implement edge type enum per algorithm

[LilithWittmann]

Currently we give our edges implicitly meaning based on context of the algorithms they are used in.

But edges have specific different meanings in different algorithms. One option would be to find a common superset between those algorithms. Another option would be to have one EdgeType enum class per Algorithm.

This could look something like this:

class PCEdgeTypes(EdgeType):
     DIRECTED_EDGE = "directed"
     UNDIRECTED_EDGE = "undirected"

     @pre
     @on_updated([PCEdgeTypes.UNDIRECTED_EDGE], [PCEdgeTypes.DIRECTED_EDGE])
     @classmethod
     def check_update_of_undirected_edge_possible(cls, node_a, node_b, graph, operations):
         pass

This also means that a PipelineStep needs to explicitly tell what kind of edge types it requires. And that the edge type enum object can be configured at the creation of a model.

[LilithWittmann]

solved with hooks.