问题描述：发现服务关停过程中未正常调用ServiceDiscovery的unregister方法

问题原因：
1. preDestroy中，先执行destroyRegistries()，再执行destroyServiceDiscoveries()，最后执行unregisterServiceInstance()
~~~
    @Override
    public void preDestroy() {
        synchronized (destroyLock) {
            if (isStopping() || isStopped()) {
                return;
            }
            onStopping();

            destroyRegistries();
            destroyServiceDiscoveries();
            destroyMetadataReports();

            unRegisterShutdownHook();
            if (asyncMetadataFuture != null) {
                asyncMetadataFuture.cancel(true);
            }
            unregisterServiceInstance();
        }
    }
~~~
2. destroyRegistries()方法中调用destroyAll()方法，将容器registries中所有Registry进行销毁并从容器registries中移除，此时容器registries中已经没有数据，并且所有与注册中心的通信工具（如nacos的NamingService，zk的CuratorFramework）都被销毁
~~~
   public void destroyAll() {
        if (!destroyed.compareAndSet(false, true)) {
            return;
        }

        if (LOGGER.isInfoEnabled()) {
            LOGGER.info("Close all registries " + getRegistries());
        }
        // Lock up the registry shutdown process
        lock.lock();
        try {
            for (Registry registry : getRegistries()) {
                try {
                    registry.destroy();
                } catch (Throwable e) {
                    LOGGER.warn(e.getMessage(), e);
                }
            }
            registries.clear();
        } finally {
            // Release the lock
            lock.unlock();
        }
    }
~~~
3. destroyServiceDiscoveries()、unregisterServiceInstance()执行时，已经无法从容器registries中获取ServiceDiscoveries（即使能获取到，与注册中心的通信工具NamingService\CuratorFramework等已经被销毁无法使用）

修改方法：将unregisterServiceInstance()调整到destroyRegistries()之前，并删除destroyServiceDiscoveries()
~~~
   @Override
    public void preDestroy() {
        synchronized (destroyLock) {
            if (isStopping() || isStopped()) {
                return;
            }
            onStopping();
            
            unregisterServiceInstance();
            destroyRegistries();
            destroyMetadataReports();

            unRegisterShutdownHook();
            if (asyncMetadataFuture != null) {
                asyncMetadataFuture.cancel(true);
            }

        }
    }
~~~

environment.updateExternalConfigMap(configCenter.getExternalConfiguration());
                environment.updateAppExternalConfigMap(configCenter.getAppExternalConfiguration());
                
                compositeDynamicConfiguration.addConfiguration(prepareEnvironment(configCenter));
            }
            environment.setDynamicConfiguration(compositeDynamicConfiguration);
        }
    }
    private void startMetadataCenter() {
        useRegistryAsMetadataCenterIfNecessary();
        ApplicationConfig applicationConfig = getApplication();
        String metadataType = applicationConfig.getMetadataType();
        
        Collection<MetadataReportConfig> metadataReportConfigs = configManager.getMetadataConfigs();
        if (CollectionUtils.isEmpty(metadataReportConfigs)) {
            if (REMOTE_METADATA_STORAGE_TYPE.equals(metadataType)) {
                throw new IllegalStateException("No MetadataConfig found, Metadata Center address is required when 'metadata=remote' is enabled.");
            }
            return;
        }
        MetadataReportInstance metadataReportInstance = applicationModel.getBeanFactory().getBean(MetadataReportInstance.class);
        List<MetadataReportConfig> validMetadataReportConfigs = new ArrayList<>(metadataReportConfigs.size());
        for (MetadataReportConfig metadataReportConfig : metadataReportConfigs) {
            ConfigValidationUtils.validateMetadataConfig(metadataReportConfig);
            validMetadataReportConfigs.add(metadataReportConfig);
        }
        metadataReportInstance.init(validMetadataReportConfigs);
        if (!metadataReportInstance.inited()) {
            throw new IllegalStateException(String.format("%s MetadataConfigs found, but none of them is valid.", metadataReportConfigs.size()));