Add Transform associated indices (elastic#69493)

These somehow got dropped from the initial Feature States PR, so this
commit adds them again.

x-pack/plugin/transform/src/main/java/org/elasticsearch/xpack/transform/Transform.java

@@ -123,6 +123,7 @@
 import java.util.function.UnaryOperator;
 
 import static java.util.Collections.emptyList;
+import static org.elasticsearch.xpack.core.transform.transforms.persistence.TransformInternalIndexConstants.AUDIT_INDEX_PATTERN;
 
 public class Transform extends Plugin implements SystemIndexPlugin, PersistentTaskPlugin {
 
@@ -397,6 +398,10 @@ public Collection<SystemIndexDescriptor> getSystemIndexDescriptors(Settings sett
         }
     }
 
+    @Override public Collection<String> getAssociatedIndexPatterns() {
+        return org.elasticsearch.common.collect.List.of(AUDIT_INDEX_PATTERN);
+    }
+
     @Override
     public String getFeatureName() {
         return "transform";