Today in a few places we create a `new CountDown(0)`. This is kind of trappy because it will never return `true` from `#countDown()` or `#fastForward()` which risks never completing whatever action needs completing unless the caller handles the empty case specially.

We should refactor the places that do this so that they all avoid creating an empty `CountDown`, instead just handling the fact that the action is already complete:

- [ ] `TransportIndicesShardStoresAction$AsyncShardStoresInfoFetches`
- [ ] `ClearScrollController`
- [ ] `TransportBroadcastReplicationAction#doExecute`
- [ ] `Realms#usageStats`

Once we've done that, we can forbid the creation of an empty `CountDown`.
server/src/main/java/org/elasticsearch/action/support/replication/TransportBroadcastReplicationAction.java
import org.elasticsearch.cluster.metadata.IndexMetadata;
import org.elasticsearch.cluster.metadata.IndexNameExpressionResolver;
import org.elasticsearch.cluster.routing.IndexRoutingTable;
import org.elasticsearch.cluster.service.ClusterService;
import org.elasticsearch.common.io.stream.Writeable;
import org.elasticsearch.common.util.concurrent.CountDown;
import org.elasticsearch.index.shard.ShardId;
import org.elasticsearch.tasks.Task;
import org.elasticsearch.transport.TransportService;
import java.util.ArrayList;
import java.util.Arrays;
import java.util.List;
import java.util.concurrent.CopyOnWriteArrayList;
/**
 * Base class for requests that should be executed on all shards of an index or several indices.
 * This action sends shard requests to all primary shards of the indices and they are then replicated like write requests
 */
public abstract class TransportBroadcastReplicationAction<
    Request extends BroadcastRequest<Request>,
    Response extends BaseBroadcastResponse,
    ShardRequest extends ReplicationRequest<ShardRequest>,
    ShardResponse extends ReplicationResponse> extends HandledTransportAction<Request, Response> {
    private final ActionType<ShardResponse> replicatedBroadcastShardAction;
    private final ClusterService clusterService;
    private final IndexNameExpressionResolver indexNameExpressionResolver;
    private final NodeClient client;
    public TransportBroadcastReplicationAction(
        String name,
        Writeable.Reader<Request> requestReader,
        ClusterService clusterService,