Refactor graph creation in all tests into new internal MakeTestGraph trait

This large refactor allows future re-use of the existing tests for `FrozenGraph`, which does not implement `GraphTopologyAddition`, but instead has to convert from a different graph which does.

- Fix tests for `GraphTopologyDeletion` hard-coding Graph instead of using the trait.
- Fix some tests silently depending on macro call site uses.
- Change `GraphTopologyAddition` tests to use `Default::default` instead of `new`.
- Add new tests for `GraphTopology::vertex_map` and `edge_map` that also depend on `GraphTopologyAddition`, removing these dependencies from the existing tests.
- Add new test macro `graph_topology_addition_deletion_tests` for tests that need deletion and addition.

tests/dijkstra.rs

@@ -1,13 +1,11 @@
 mod append_graph_tests {
     use grapherity::models::AppendGraph;
 
-    grapherity::graph_topology_test_fixtures!(AppendGraph);
     grapherity::dijkstra_tests!(AppendGraph);
 }
 
 mod graph_tests {
     use grapherity::models::Graph;
 
-    grapherity::graph_topology_test_fixtures!(Graph);
     grapherity::dijkstra_tests!(Graph);
 }