KAFKA-15186 AppInfo metrics don't contain the client-id

[m1a2st]

All Kafka component register AppInfo metrics to track the application
start time or commit-id etc. These metrics are useful for monitoring and
debugging. However, the AppInfo doesn't provide client-id, which is an
important information for custom metrics reporter.

The AppInfoParser class registers a JMX MBean with the provided
client-id, but when it adds metrics to the Metrics registry, the
client-id is not included. This KIP aims to add the client-id as a tag.

[chia7712]

please remove the indent.

[chia7712]

Could you please move this condition into registerMetrics? for example:

    public static synchronized void unregisterAppInfo(String prefix, String id, Metrics metrics) {
        MBeanServer server = ManagementFactory.getPlatformMBeanServer();
        try {
            ObjectName name = new ObjectName(prefix + ":type=app-info,id=" + Sanitizer.jmxSanitize(id));
            if (server.isRegistered(name))
                server.unregisterMBean(name);

            unregisterMetrics(metrics, id);
        } catch (JMException e) {
            log.warn("Error unregistering AppInfo mbean", e);
        } finally {
            log.info("App info {} for {} unregistered", prefix, id);
        }
    }

    private static void registerMetrics(Metrics metrics, AppInfo appInfo, String clientId) {
        if (metrics == null) return;

        // add comments for this case
        metrics.addMetric(metricName(metrics, "version", Map.of()), (Gauge<String>) (config, now) -> appInfo.getVersion());
        metrics.addMetric(metricName(metrics, "commit-id", Map.of()), (Gauge<String>) (config, now) -> appInfo.getCommitId());
        metrics.addMetric(metricName(metrics, "start-time-ms", Map.of()), (Gauge<Long>) (config, now) -> appInfo.getStartTimeMs());

        // add comments for this case
        if (!metrics.config().tags().containsKey("client-id")) {
            metrics.addMetric(metricName(metrics, "version", Map.of("client-id", clientId)), (Gauge<String>) (config, now) -> appInfo.getVersion());
            metrics.addMetric(metricName(metrics, "commit-id", Map.of("client-id", clientId)), (Gauge<String>) (config, now) -> appInfo.getCommitId());
            metrics.addMetric(metricName(metrics, "start-time-ms", Map.of("client-id", clientId)), (Gauge<Long>) (config, now) -> appInfo.getStartTimeMs());
        }
    }

[chia7712]

if (!metrics.config().tags().containsKey("client-id")) may need to include clientId != null