[improve][broker] Use immutable base cursor properties (apache#20400)

Author: lhotari

pulsar-broker/src/main/java/org/apache/pulsar/broker/service/persistent/PersistentSubscription.java

@@ -120,18 +120,15 @@ public class PersistentSubscription extends AbstractSubscription implements Subs
     // Map of properties that is used to mark this subscription as "replicated".
     // Since this is the only field at this point, we can just keep a static
     // instance of the map.
-    private static final Map<String, Long> REPLICATED_SUBSCRIPTION_CURSOR_PROPERTIES = new TreeMap<>();
-    private static final Map<String, Long> NON_REPLICATED_SUBSCRIPTION_CURSOR_PROPERTIES = Collections.emptyMap();
+    private static final Map<String, Long> REPLICATED_SUBSCRIPTION_CURSOR_PROPERTIES =
+            Map.of(REPLICATED_SUBSCRIPTION_PROPERTY, 1L);
+    private static final Map<String, Long> NON_REPLICATED_SUBSCRIPTION_CURSOR_PROPERTIES = Map.of();
 
     private volatile ReplicatedSubscriptionSnapshotCache replicatedSubscriptionSnapshotCache;
     private final PendingAckHandle pendingAckHandle;
     private volatile Map<String, String> subscriptionProperties;
     private volatile CompletableFuture<Void> fenceFuture;
 
-    static {
-        REPLICATED_SUBSCRIPTION_CURSOR_PROPERTIES.put(REPLICATED_SUBSCRIPTION_PROPERTY, 1L);
-    }
-
     static Map<String, Long> getBaseCursorProperties(boolean isReplicated) {
         return isReplicated ? REPLICATED_SUBSCRIPTION_CURSOR_PROPERTIES : NON_REPLICATED_SUBSCRIPTION_CURSOR_PROPERTIES;
     }