### Elasticsearch Version

All

### Installed Plugins

N/A

### Java Version

_bundled_

### OS Version

N/A

### Problem Description

Today if an index has an `index.auto_expand_replicas` setting which cannot be realised in the cluster then the number of replicas is left unchanged by `AllocationService#adaptAutoExpandReplicas()`. Instead, I think we should change the number of replicas to the closest value within the permitted range.

For instance: if a cluster has a single data node which is marked as shutting down for restart then auto-expand replicas considers this cluster to have zero data nodes, and hence requires -1 replicas. If an index is created with `index.auto_expand_replicas: "0-1"` then it will not be adjusted to have zero replicas, even though this would be better than leaving it at the default value of 1 replica, and will ultimately be the correct setting.

### Steps to Reproduce

1. Create a cluster with one data node.
2. Put a `RESTART` shutdown marker on the data node.
3. Create an index with `index.auto_expand_replicas: "0-1"`
4. Observe that this results in an unassigned replica.

### Logs (if relevant)

_No response_
server/src/test/java/org/elasticsearch/cluster/metadata/AutoExpandReplicasTests.java
import org.elasticsearch.action.support.ActiveShardCount;
import org.elasticsearch.action.support.replication.ClusterStateCreationUtils;
import org.elasticsearch.cluster.ClusterState;
import org.elasticsearch.cluster.node.DiscoveryNode;
import org.elasticsearch.cluster.node.DiscoveryNodeRole;
import org.elasticsearch.cluster.node.DiscoveryNodes;
import org.elasticsearch.cluster.routing.IndexShardRoutingTable;
import org.elasticsearch.cluster.routing.RoutingNodesHelper;
import org.elasticsearch.cluster.routing.ShardRoutingState;
import org.elasticsearch.common.settings.Settings;
import org.elasticsearch.indices.cluster.ClusterStateChanges;
import org.elasticsearch.test.ESTestCase;
import org.elasticsearch.test.VersionUtils;
import org.elasticsearch.threadpool.TestThreadPool;
import org.elasticsearch.threadpool.ThreadPool;
import java.util.ArrayList;
import java.util.Collections;
import java.util.HashSet;
import java.util.List;
import java.util.Locale;
import java.util.Set;
import java.util.concurrent.atomic.AtomicInteger;
import java.util.stream.Collectors;
import static org.elasticsearch.cluster.metadata.IndexMetadata.SETTING_AUTO_EXPAND_REPLICAS;
import static org.elasticsearch.cluster.metadata.IndexMetadata.SETTING_NUMBER_OF_SHARDS;
import static org.hamcrest.Matchers.equalTo;
import static org.hamcrest.Matchers.everyItem;
import static org.hamcrest.Matchers.in;
import static org.hamcrest.Matchers.is;
public class AutoExpandReplicasTests extends ESTestCase {