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/gcore/src/storage.rs

@@ -82,10 +82,10 @@ where
 
 #[cfg(test)]
 mod test {
+	use super::*;
 	use crate::value::{CopiedNode, OnceCellNode};
 	use crate::Node;
 
-	use super::*;
 	#[test]
 	fn get_node_array() {
 		let storage = [1, 2, 3];