Implement source maps between proto/document nodes

Add the node path to the document node and carry that over to the proto
nodes which are generated from that.
This pr also adds a compiler pass to assign the paths based on the
hierarchical structure of the nodegraph.

Test Plan: - Run units tests which check the path propagation works

Reviewers: Keavon

Reviewed By: Keavon

Pull Request: https://github.com/GraphiteEditor/Graphite/pull/1181

node-graph/compilation-client/src/main.rs

@@ -58,8 +58,8 @@ fn add_network() -> NodeNetwork {
 				DocumentNode {
 					name: "Dup".into(),
 					inputs: vec![NodeInput::value(value::TaggedValue::U32(5u32), false)],
-					metadata: DocumentNodeMetadata::default(),
 					implementation: DocumentNodeImplementation::Unresolved(NodeIdentifier::new("graphene_core::ops::IdNode")),
+					..Default::default()
 				},
 			),
 			// (