This turned out to be a big messy commit, since the way providers are
referenced is tightly coupled throughout the code. That starts to unify
how providers are referenced, using the format output node Name method.
Add a new field to the internal resource data types called
ResolvedProvider. This is set by a new setter method SetProvider when a
resource is connected to a provider during graph creation. This allows
us to later lookup the provider instance a resource is connected to,
without requiring it to have the same module path.
The InitProvider context method now takes 2 arguments, one if the
provider type and the second is the full name of the provider. While the
provider type could still be parsed from the full name, this makes it
more explicit and, and changes to the name format won't effect this
code.
DestroyValueReferenceTransformer is used during destroy to reverse the
edges for output and local values. Because destruction is going to
remove these from the state, nodes that depend on their value need to be
visited first.
A local value is similar to an output in that it exists only within state
and just always evaluates its value as best it can with the current state.
Therefore it has a single graph node type for all walks, which will
deal with that evaluation operation.
terraform: more specific resource references
terraform: outputs need to know about the new reference format
terraform: resources w/o a config still have a referencable name
