KAFKA-19504: Remove unused metrics reporter initialization in KafkaAdminClient (#20166)

The `AdminClient` adds a telemetry reporter to the metrics reporters
list in the constructor.  The problem is that the reporter was already
added in the `createInternal` method.  In the `createInternal` method
call, the `clientTelemetryReporter` is added to a
`List<MetricReporters>` which is passed to the `Metrics` object, will
get closed when `Metrics.close()` is called.  But adding a reporter to
the reporters list in the constructor is not used by the `Metrics`
object and hence doesn't get closed, causing a memory leak.

All related tests pass after this change.

Reviewers: Apoorv Mittal <[email protected]>, Matthias J. Sax
 <[email protected]>, Chia-Ping Tsai <[email protected]>,
 Jhen-Yung Hsu <[email protected]>

Author: bbejeck

clients/src/main/java/org/apache/kafka/clients/admin/KafkaAdminClient.java

@@ -577,10 +577,12 @@ static KafkaAdminClient createInternal(AdminClientConfig config,
                                            Time time) {
         Metrics metrics = null;
         String clientId = generateClientId(config);
+        List<MetricsReporter> reporters = CommonClientConfigs.metricsReporters(clientId, config);
         Optional<ClientTelemetryReporter> clientTelemetryReporter = CommonClientConfigs.telemetryReporter(clientId, config);
+        clientTelemetryReporter.ifPresent(reporters::add);
 
         try {
-            metrics = new Metrics(new MetricConfig(), new LinkedList<>(), time);
+            metrics = new Metrics(new MetricConfig(), reporters, time);
             LogContext logContext = createLogContext(clientId);
             return new KafkaAdminClient(config, clientId, time, metadataManager, metrics,
                 client, null, logContext, clientTelemetryReporter);
@@ -625,9 +627,7 @@ private KafkaAdminClient(AdminClientConfig config,
             CommonClientConfigs.RETRY_BACKOFF_EXP_BASE,
             retryBackoffMaxMs,
             CommonClientConfigs.RETRY_BACKOFF_JITTER);
-        List<MetricsReporter> reporters = CommonClientConfigs.metricsReporters(this.clientId, config);
         this.clientTelemetryReporter = clientTelemetryReporter;
-        this.clientTelemetryReporter.ifPresent(reporters::add);
         this.metadataRecoveryStrategy = MetadataRecoveryStrategy.forName(config.getString(AdminClientConfig.METADATA_RECOVERY_STRATEGY_CONFIG));
         this.partitionLeaderCache = new HashMap<>();
         this.adminFetchMetricsManager = new AdminFetchMetricsManager(metrics);