[ISSUE #11994]修复HttpRequestInstanceBuilderTest出现的空指针问题，优化SnowFlakeInstanceIdGenerator初始化流程 (#11995)

* [ISSUE #11994] fix: Initialize EnvUtil's variable environment in HttpRequestInstanceBuilderTest

* refactor: Optimize the initialization process of SnowFlakeInstanceIdGenerator

* refactor: optimize the initialization process of SnowFlakeInstanceIdGenerator.

naming/src/main/java/com/alibaba/nacos/naming/pojo/instance/SnowFlakeInstanceIdGenerator.java

@@ -31,13 +31,28 @@ import static com.alibaba.nacos.api.common.Constants.SNOWFLAKE_INSTANCE_ID_GENER
 public class SnowFlakeInstanceIdGenerator implements InstanceIdGenerator {
     
     private static final SnowFlowerIdGenerator SNOW_FLOWER_ID_GENERATOR = new SnowFlowerIdGenerator();
-    
-    static {
-        SNOW_FLOWER_ID_GENERATOR.init();
+
+    private static volatile boolean initialize = false;
+
+    private static final Object LOCK = new Object();
+
+    /**
+     * initialize the workerId and ensure that it is only initialized once.
+     */
+    private void ensureWorkerIdInitialization() {
+        if (!initialize) {
+            synchronized (LOCK) {
+                if (!initialize) {
+                    SNOW_FLOWER_ID_GENERATOR.init();
+                    initialize = true;
+                }
+            }
+        }
     }
-    
+
     @Override
     public String generateInstanceId(Instance instance) {
+        ensureWorkerIdInitialization();
         return SNOW_FLOWER_ID_GENERATOR.nextId() + NAMING_INSTANCE_ID_SPLITTER
                 + instance.getClusterName() + NAMING_INSTANCE_ID_SPLITTER
                 + instance.getServiceName();

naming/src/test/java/com/alibaba/nacos/naming/pojo/instance/HttpRequestInstanceBuilderTest.java

@@ -21,12 +21,14 @@ import com.alibaba.nacos.api.naming.CommonParams;
 import com.alibaba.nacos.api.naming.pojo.Instance;
 import com.alibaba.nacos.common.spi.NacosServiceLoader;
 import com.alibaba.nacos.naming.misc.UtilsAndCommons;
+import com.alibaba.nacos.sys.env.EnvUtil;
 import org.junit.Before;
 import org.junit.BeforeClass;
 import org.junit.Test;
 import org.junit.runner.RunWith;
 import org.mockito.Mock;
 import org.mockito.junit.MockitoJUnitRunner;
+import org.springframework.core.env.StandardEnvironment;
 
 import javax.servlet.http.HttpServletRequest;
 
@@ -54,6 +56,7 @@ public class HttpRequestInstanceBuilderTest {
     @BeforeClass
     public static void setUpBeforeClass() {
         NacosServiceLoader.load(InstanceExtensionHandler.class);
+        EnvUtil.setEnvironment(new StandardEnvironment());
     }
     
     @Before