Code cleanup and refactoring to enhance consistency (#1695)

- Move message handler payload data into structs
- Organize the file structure used by `editor/src/messages/portfolio/document` `/node_graph` and `/graph_operation`
- Make derive attributes use `serde::Serialize, serde::Deserialize` consistently instead of `use serde::{Deserialize, Serialize};` imports
- Various other code cleanup and refactoring

node-graph/graph-craft/src/document.rs

@@ -1233,12 +1233,13 @@ impl<'a> Iterator for RecursiveNodeIter<'a> {
 
 #[cfg(test)]
 mod test {
-	use std::sync::atomic::AtomicU64;
-
 	use super::*;
 	use crate::proto::{ConstructionArgs, ProtoNetwork, ProtoNode, ProtoNodeInput};
+
 	use graphene_core::ProtoNodeIdentifier;
 
+	use std::sync::atomic::AtomicU64;
+
 	fn gen_node_id() -> NodeId {
 		static NODE_ID: AtomicU64 = AtomicU64::new(4);
 		NodeId(NODE_ID.fetch_add(1, std::sync::atomic::Ordering::SeqCst))