adjust `add_edges()` and related functions to `get_edge_ids()`

[schochastics]

get_edge_ids() allows nx2 matrices and data frames now for the edge attribute. Once #1798 is settled, these changes need to also be applied to:

• add_edges()
• delete_edges() delete_edges bug and counterintuitive add_edges behaviour (and workaround) #550
• edge()/edges() delete_edges bug and counterintuitive add_edges behaviour (and workaround) #550

[maelle]

Noting that #1798 should be ready soon.