test(logging): centralize test prefix handling inside RemoteLoggingHelper

Embeds TEST_SINK_PREFIX directly within RemoteLoggingHelper.formatForTest(), ensuring all client test cases across the entire test suite consistently receive standardized prefix formatting without requiring class-local wrappers or repetitive literal string prefixes.

BUG=b/482174880
TAG=agy
CONV=d4a74f94-579a-4c3f-96c3-f90fcbc6c699

Author: lqiu96

java-logging/google-cloud-logging/src/main/java/com/google/cloud/logging/testing/RemoteLoggingHelper.java

@@ -37,6 +37,7 @@
 public class RemoteLoggingHelper {
 
   private static final Logger log = Logger.getLogger(RemoteLoggingHelper.class.getName());
+  private static final String TEST_SINK_PREFIX = "test-";
   private final LoggingOptions options;
 
   private RemoteLoggingHelper(LoggingOptions options) {
@@ -96,7 +97,8 @@ public static RemoteLoggingHelper create() {
    * name.
    */
   public static String formatForTest(String name) {
-    return name + "-" + UUID.randomUUID();
+    String prefix = name.startsWith(TEST_SINK_PREFIX) ? "" : TEST_SINK_PREFIX;
+    return prefix + name + "-" + UUID.randomUUID();
   }
 
   private static RetrySettings retrySettings() {

java-logging/google-cloud-logging/src/test/java/com/google/cloud/logging/it/ITSinkTest.java

@@ -16,6 +16,7 @@
 
 package com.google.cloud.logging.it;
 
+import static com.google.cloud.logging.testing.RemoteLoggingHelper.formatForTest;
 import static org.junit.Assert.assertEquals;
 import static org.junit.Assert.assertFalse;
 import static org.junit.Assert.assertNotNull;
@@ -29,7 +30,6 @@
 import com.google.cloud.logging.LoggingException;
 import com.google.cloud.logging.Sink;
 import com.google.cloud.logging.SinkInfo;
-import com.google.cloud.logging.testing.RemoteLoggingHelper;
 import com.google.common.collect.Sets;
 import java.util.Iterator;
 import java.util.Set;
@@ -40,10 +40,6 @@ public class ITSinkTest extends BaseSystemTest {
 
   private static final String TEST_SINK_PREFIX = "test-";
 
-  private static String formatForTest(String name) {
-    return RemoteLoggingHelper.formatForTest(TEST_SINK_PREFIX + name);
-  }
-
   @BeforeClass
   public static void setUp() {
     // Cleanup all stucked sinks if any