Massively reorganize and clean up the whole Rust codebase (#478)

* Massively reorganize and clean up the whole Rust codebase

* Additional changes during code review

editor/src/document/transform_layer_message.rs

@@ -0,0 +1,22 @@
+use crate::input::keyboard::Key;
+use crate::message_prelude::*;
+
+use serde::{Deserialize, Serialize};
+
+#[remain::sorted]
+#[impl_message(Message, DocumentMessage, TransformLayers)]
+#[derive(PartialEq, Clone, Debug, Serialize, Deserialize)]
+pub enum TransformLayerMessage {
+	ApplyTransformOperation,
+	BeginGrab,
+	BeginRotate,
+	BeginScale,
+	CancelTransformOperation,
+	ConstrainX,
+	ConstrainY,
+	MouseMove { slow_key: Key, snap_key: Key },
+	TypeBackspace,
+	TypeDecimalPoint,
+	TypeNegate,
+	TypeNumber(u8),
+}