Add lax::open_hypergraph function to delete an edge

[mstn]

• Feature in Add lax::open_hypergraph function to delete an edge #13
• Changed panic behavior in delete_nodes to be aligned with delete_edges. Rationale: better to fail hard than swallow errors. Technically, it is a breaking change but I don't think we should document it (edge case + nobody uses delete_nodes yet).

[statusfailed]

Agreed on panic behaviour, thanks for pointing this out!

FYI: for future tests you can use the new_edge method instead of creating the adjacency array manually, e.g.:

      let mut h = OpenHypergraph::empty();
      let x0 = h.new_node(node_label);
      let x1 = h.new_node(node_label);
      let x2 = h.new_node(node_label);

      state.new_edge(edge_label, ([x0, x1], [x2]));