Simplify Subresource Saving

Redo edited subresource (and resource) saving in a much more simplified way.
I think this should work (unless I am missing something) and be faster than what is there.
It should also supersede #55885.

I am not 100% entirely convinced that this approach works, but I think it should so please test.

(cherry picked from commit 9eb5f2a0d79fb761235e77d369ee2f38fceb094a)

editor/editor_node.cpp

@@ -1439,34 +1439,6 @@ bool EditorNode::_validate_scene_recursive(const String &p_filename, Node *p_nod
 	return false;
 }
 
-static bool _find_edited_resources(const Ref<Resource> &p_resource, Set<Ref<Resource>> &edited_resources) {
-	if (p_resource->is_edited()) {
-		edited_resources.insert(p_resource);
-		return true;
-	}
-
-	List<PropertyInfo> plist;
-
-	p_resource->get_property_list(&plist);
-
-	for (List<PropertyInfo>::Element *E = plist.front(); E; E = E->next()) {
-		if (E->get().type == Variant::OBJECT && E->get().usage & PROPERTY_USAGE_STORAGE && !(E->get().usage & PROPERTY_USAGE_RESOURCE_NOT_PERSISTENT)) {
-			RES res = p_resource->get(E->get().name);
-			if (res.is_null()) {
-				continue;
-			}
-			if (res->get_path().is_resource_file()) { //not a subresource, continue
-				continue;
-			}
-			if (_find_edited_resources(res, edited_resources)) {
-				return true;
-			}
-		}
-	}
-
-	return false;
-}
-
 int EditorNode::_save_external_resources() {
 	//save external resources and its subresources if any was modified
 
@@ -1476,30 +1448,43 @@ int EditorNode::_save_external_resources() {
 	}
 	flg |= ResourceSaver::FLAG_REPLACE_SUBRESOURCE_PATHS;
 
-	Set<Ref<Resource>> edited_subresources;
+	Set<String> edited_resources;
 	int saved = 0;
 	List<Ref<Resource>> cached;
 	ResourceCache::get_cached_resources(&cached);
 	for (List<Ref<Resource>>::Element *E = cached.front(); E; E = E->next()) {
 		Ref<Resource> res = E->get();
-		if (!res->get_path().is_resource_file()) {
+		if (!res->is_edited()) {
 			continue;
 		}
-		//not only check if this resourec is edited, check contained subresources too
-		if (_find_edited_resources(res, edited_subresources)) {
-			ResourceSaver::save(res->get_path(), res, flg);
-			saved++;
-		}
-	}
 
-	// clear later, because user may have put the same subresource in two different resources,
-	// which will be shared until the next reload
+		String path = res->get_path();
+		if (path.begins_with("res://")) {
+			int subres_pos = path.find("::");
+			if (subres_pos == -1) {
+				// Actual resource.
+				edited_resources.insert(path);
+			} else {
+				edited_resources.insert(path.substr(0, subres_pos));
+			}
+		}
 
-	for (Set<Ref<Resource>>::Element *E = edited_subresources.front(); E; E = E->next()) {
-		Ref<Resource> res = E->get();
 		res->set_edited(false);
 	}
 
+	for (Set<String>::Element *E = edited_resources.front(); E; E = E->next()) {
+		Ref<Resource> res = Ref<Resource>(ResourceCache::get(E->get()));
+		if (!res.is_valid()) {
+			continue; // Maybe it was erased in a thread, who knows.
+		}
+		Ref<PackedScene> ps = res;
+		if (ps.is_valid()) {
+			continue; // Do not save PackedScenes, this will mess up the editor.
+		}
+		ResourceSaver::save(res->get_path(), res, flg);
+		saved++;
+	}
+
 	return saved;
 }