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

editor/src/messages/workspace/workspace_message.rs

@@ -1,9 +1,7 @@
 use crate::messages::prelude::*;
 
-use serde::{Deserialize, Serialize};
-
 #[impl_message(Message, Workspace)]
-#[derive(PartialEq, Eq, Clone, Debug, Serialize, Deserialize)]
+#[derive(PartialEq, Eq, Clone, Debug, serde::Serialize, serde::Deserialize)]
 pub enum WorkspaceMessage {
 	// Messages
 	NodeGraphToggleVisibility,

editor/src/messages/workspace/workspace_message_handler.rs

@@ -7,11 +7,9 @@ pub struct WorkspaceMessageHandler {
 
 impl MessageHandler<WorkspaceMessage, ()> for WorkspaceMessageHandler {
 	fn process_message(&mut self, message: WorkspaceMessage, _responses: &mut VecDeque<Message>, _data: ()) {
-		use WorkspaceMessage::*;
-
 		match message {
 			// Messages
-			NodeGraphToggleVisibility => {
+			WorkspaceMessage::NodeGraphToggleVisibility => {
 				self.node_graph_visible = !self.node_graph_visible;
 			}
 		}