[fix] [broker] do not filter system topic while shedding. (#18949)

### Motivation

Currently, topics/bundles in `pulsar/system` will be filter while doing shedding, which is introduced by mistake by pr #15252.
But we need to unload topics/bundles in `pulsar/system` for load balancing. 

### Modifications

do not filter topics/bundles in `pulsar/system`.

pulsar-broker/src/main/java/org/apache/pulsar/broker/loadbalance/LoadData.java

@@ -64,7 +64,7 @@ public Map<String, BundleData> getBundleData() {
 
     public Map<String, BundleData> getBundleDataForLoadShedding() {
         return bundleData.entrySet().stream()
-                .filter(e -> !NamespaceService.isSystemServiceNamespace(
+                .filter(e -> !NamespaceService.filterNamespaceForShedding(
                         NamespaceBundle.getBundleNamespace(e.getKey())))
                 .collect(Collectors.toMap(Map.Entry::getKey, Map.Entry::getValue));
     }

pulsar-broker/src/main/java/org/apache/pulsar/broker/namespace/NamespaceService.java

@@ -1607,6 +1607,17 @@ public static boolean isSystemServiceNamespace(String namespace) {
                 || HEARTBEAT_NAMESPACE_PATTERN_V2.matcher(namespace).matches();
     }
 
+    /**
+     * used for filtering bundles in special namespace.
+     * @param namespace
+     * @return True if namespace is HEARTBEAT_NAMESPACE or SLA_NAMESPACE
+     */
+    public static boolean filterNamespaceForShedding(String namespace) {
+        return SLA_NAMESPACE_PATTERN.matcher(namespace).matches()
+                || HEARTBEAT_NAMESPACE_PATTERN.matcher(namespace).matches()
+                || HEARTBEAT_NAMESPACE_PATTERN_V2.matcher(namespace).matches();
+    }
+
     public static boolean isHeartbeatNamespace(ServiceUnitId ns) {
         String namespace = ns.getNamespaceObject().toString();
         return HEARTBEAT_NAMESPACE_PATTERN.matcher(namespace).matches()