@VisibleForTesting
        synchronized CompletableFuture<ElasticLogMeta> getPendingPersistentMetaCf() {
            return pendingPersistentMetaCf;
        }
Calculate trim offset of each stream.

@return stream trim offset map, key is stream name, value is trim offset.
core/src/main/scala/kafka/log/streamaspect/ElasticLogSegmentManager.java