downstream test from sdk-platform-java for pubsublite multiple tests flaky

full log [here](https://github.com/googleapis/sdk-platform-java/actions/runs/15394245857/job/43312465340?pr=3804)
```
Error: Errors:
Error: AckSetTrackerImplTest.trackAndAggregateAcks:94 » NullPointer Cannot invoke "com.google.api.core.ApiFuture.addListener(java.lang.Runnable, java.util.concurrent.Executor)" because "future" is null
Error: SinglePartitionPublisherTest.publishResultTransformed:91 WrongTypeOfReturnValue
```
another rerun [log](https://github.com/googleapis/sdk-platform-java/actions/runs/15394245857/job/43310805083?pr=3804)
```
Error: Errors:
Error: SinglePartitionSubscriberTest.singleMessageNackHandlerFailedFuture:228 » IllegalState failureCause() is only valid if the service has failed, service is RUNNING
```

Inizia dai log collegati di sdk-platform-java e dai test falliti AckSetTrackerImplTest.trackAndAggregateAcks, SinglePartitionPublisherTest.publishResultTransformed e SinglePartitionSubscriberTest.singleMessageNackHandlerFailedFuture alle righe indicate. Riproduci i fallimenti e determina perché questi test sono flaky; il lavoro è completato quando i test interessati superano in modo affidabile le esecuzioni ripetute.

Scritto dal modello di indicizzazione a partire dal testo della issue.