trackbone: handle destroy targets in graph
When using a diff to generate the graph some targets may have to be destroy while others have to be applied.
In the case of destroying an env, all the env configs have a destroy action but some other configurations in other envs may need to be applied because the env is removed.
When building the graph we simply inverse the arcs for destroyed configurations.
When generating a graph from a diff the destroy global action is not relevant. It is only possible to plan or apply a diff.