Add the "memoize" attribute to the node macro (#4065)

* Add memoization attribute to node macro

* Fix memoization insertion for networks without conversion nodes

node-graph/libraries/core-types/src/registry.rs

@@ -16,6 +16,7 @@ pub struct NodeMetadata {
 	pub description: &'static str,
 	pub properties: Option<&'static str>,
 	pub context_features: Vec<ContextFeature>,
+	pub memoize: bool,
 }
 
 // Translation struct between macro and definition