Replace usage of connected_nodes during the refactoring

[antonykamp]

During the refactoring See simulate-digital-rail/yaramo#40 we have to replace writing access of connected_nodes with connected_edges and edit calls of set_connection_left, set_connection_right and set_connection_head to take edges instead of nodes.

Acceptance criterion

• Replace writing access of connected_nodes with connected_edges
• Give set_connection_left the edge instead of a node
• Give set_connection_right the edge instead of a node
• Give set_connection_head the edge instead of a node

[antonykamp]

I was trying to implement the refactored version of Yaramo. But I couldn't figure the example out:
https://github.com/simulate-digital-rail/interlocking-exporter/blob/main/examples/example.py
Please verify that the graph at the top of the file equals the code. 🙃
Thank you!

[Lietze]

I think from line 36 to 38 the connections of node d are being set again. Before, it seems to me like the graph is actuate, but this changes where d is. These are the lines:

    node_d.set_connection_left(node_c)
    node_d.set_connection_right(node_f)
    node_d.set_connection_head(node_e)

It also seems to me like there are way too many edges. I think you just have to radically cut out many of them. One edge for each connection should be enough. If that does not work, I would also try to keep edges for both directions, even though I am relatively sure that Yaramo does not need that.