Add ::IDENTITY to node macro to return a ProtoNodeIdentifier that is always a &'static str (#2842)

* fix warnings on master

* make the `ProtoNodeIdentifier` of a Node be accessible and always a borrowed `&'static str`

* always generate `node_name::identifier()`, even with `skip_impl`

* make `FrontendNodeType` use Cow

* remove broken `DocumentNodeDefinition`s for old GPU nodes

* don't reexport `graphic_element` in it's entirety, only data structures

* adjust everything to use the new `node_name::identifier()`

* fixup imports for wasm

* turn identifier fn into a constant

node-graph/gcore/src/memo.rs

@@ -2,6 +2,7 @@ use crate::{Node, WasmNotSend};
 use dyn_any::DynFuture;
 use std::future::Future;
 use std::hash::DefaultHasher;
+use std::hash::{Hash, Hasher};
 use std::ops::Deref;
 use std::sync::Arc;
 use std::sync::Mutex;
@@ -49,6 +50,10 @@ impl<T, CachedNode> MemoNode<T, CachedNode> {
 	}
 }
 
+pub mod memo {
+	pub const IDENTIFIER: crate::ProtoNodeIdentifier = crate::ProtoNodeIdentifier::new("graphene_core::memo::MemoNode");
+}
+
 /// Caches the output of a given Node and acts as a proxy.
 /// In contrast to the regular `MemoNode`. This node ignores all input.
 /// Using this node might result in the document not updating properly,
@@ -98,6 +103,10 @@ impl<T, I, CachedNode> ImpureMemoNode<I, T, CachedNode> {
 	}
 }
 
+pub mod impure_memo {
+	pub const IDENTIFIER: crate::ProtoNodeIdentifier = crate::ProtoNodeIdentifier::new("graphene_core::memo::ImpureMemoNode");
+}
+
 /// Stores both what a node was called with and what it returned.
 #[derive(Clone, Debug)]
 pub struct IORecord<I, O> {
@@ -142,7 +151,10 @@ impl<I, T, N> MonitorNode<I, T, N> {
 	}
 }
 
-use std::hash::{Hash, Hasher};
+pub mod monitor {
+	pub const IDENTIFIER: crate::ProtoNodeIdentifier = crate::ProtoNodeIdentifier::new("graphene_core::memo::MonitorNode");
+}
+
 #[derive(Clone, Copy, PartialEq, Eq, PartialOrd, Ord, Debug)]
 pub struct MemoHash<T: Hash> {
 	hash: u64,