Change listeners in Catalog from List to Set

makes more sense as the same listener should not be added twice. Also faster remove op.

Author: FlorentinD

core/src/main/java/org/neo4j/gds/core/loading/GraphStoreCatalog.java

@@ -28,12 +28,12 @@
 import org.neo4j.gds.utils.StringJoining;
 import org.neo4j.logging.Log;
 
-import java.util.ArrayList;
-import java.util.List;
+import java.util.HashSet;
 import java.util.Locale;
 import java.util.Map;
 import java.util.NoSuchElementException;
 import java.util.Optional;
+import java.util.Set;
 import java.util.concurrent.ConcurrentHashMap;
 import java.util.function.Consumer;
 import java.util.stream.Collectors;
@@ -45,7 +45,7 @@ public final class GraphStoreCatalog {
 
     private static final ConcurrentHashMap<String, UserCatalog> userCatalogs = new ConcurrentHashMap<>();
 
-    private static final List<GraphStoreCatalogListener> listeners = new ArrayList<>();
+    private static final Set<GraphStoreCatalogListener> listeners = new HashSet<>();
 
     // as we want to use the Neo4j log if possible and the catalog is a static instance,
     // we make the log injectable