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

editor/src/messages/tool/tool_messages/brush_tool.rs

@@ -311,6 +311,7 @@ fn add_brush_render(data: &BrushToolData, tool_data: &DocumentToolData, response
 		],
 		implementation: DocumentNodeImplementation::Unresolved("graphene_std::brush::BrushNode".into()),
 		metadata: graph_craft::document::DocumentNodeMetadata { position: (8, 4).into() },
+		..Default::default()
 	};
 	let mut network = NodeNetwork::value_network(brush_node);
 	network.push_output_node();