test(spanner): restrict pagination test to explicitly created database

The `ITBackupTest.testPagination` method previously listed all backups on the instance and asserted that only a single page of results would be returned (`assertFalse(page.hasNextPage())`). When running on shared integration test instances (`spanner.testenv.instance`), this assertion would fail if backups from other test runs were present on the instance.

This commit updates the pagination API calls to use `Options.filter("database:" + databaseId)`, ensuring that the test only paginates over the backups associated with the uniquely generated database for the active test run. This prevents the test from failing due to unrelated backups in the shared test environment.

Author: sakthivelmanii

java-spanner/google-cloud-spanner/src/test/java/com/google/cloud/spanner/it/slow/ITBackupTest.java

@@ -705,17 +705,26 @@ private void testUpdateBackup(Backup backup) {
     assertEquals(tomorrow, backup.getExpireTime());
   }
 
-  private void testPagination() {
+  private void testPagination(Database database) {
     logger.info("Listing backups using pagination");
 
     // First get all current backups without using pagination so we can compare that list with
     // the same list when pagination fails.
     List<Backup> initialBackups =
-        Lists.newArrayList(dbAdminClient.listBackups(instanceId).iterateAll());
+        Lists.newArrayList(
+            dbAdminClient
+                .listBackups(
+                    instanceId,
+                    Options.filter(String.format("database:%s", database.getId().getName())))
+                .iterateAll());
 
     int numBackups = 0;
     logger.info("Fetching first page");
-    Page<Backup> page = dbAdminClient.listBackups(instanceId, Options.pageSize(1));
+    Page<Backup> page =
+        dbAdminClient.listBackups(
+            instanceId,
+            Options.filter(String.format("database:%s", database.getId().getName())),
+            Options.pageSize(1));
     assertEquals(1, Iterables.size(page.getValues()));
     numBackups++;
     assertFalse(page.hasNextPage());
@@ -745,11 +754,14 @@ private void testPagination() {
       seenPageTokens.add(page.getNextPageToken());
       page =
           dbAdminClient.listBackups(
-              instanceId, Options.pageToken(page.getNextPageToken()), Options.pageSize(1));
+              instanceId,
+              Options.filter(String.format("database:%s", database.getId().getName())),
+              Options.pageToken(page.getNextPageToken()),
+              Options.pageSize(1));
       assertEquals(1, Iterables.size(page.getValues()));
       numBackups++;
     }
-    assertTrue(numBackups >= 1);
+    assertEquals(initialBackups.size(), numBackups);
   }
 
   private void testRestore(Backup backup, Timestamp versionTime, String expectedKey)