### 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/main/java/org/elasticsearch/cluster/metadata/AutoExpandReplicas.java
public static final Setting<AutoExpandReplicas> SETTING = new Setting<>(
        IndexMetadata.SETTING_AUTO_EXPAND_REPLICAS,
        "false",
        AutoExpandReplicas::parse,
        Property.Dynamic,
        Property.IndexScope
    );
    private static AutoExpandReplicas parse(String value) {
        final int min;
        final int max;
        if (Booleans.isFalse(value)) {
            return FALSE_INSTANCE;
        }
        final int dash = value.indexOf('-');
        if (-1 == dash) {
            throw new IllegalArgumentException(
                "failed to parse [" + IndexMetadata.SETTING_AUTO_EXPAND_REPLICAS + "] from value: [" + value + "] at index " + dash
            );
        }
        final String sMin = value.substring(0, dash);
        try {
            min = Integer.parseInt(sMin);
        } catch (NumberFormatException e) {
            throw new IllegalArgumentException(
                "failed to parse [" + IndexMetadata.SETTING_AUTO_EXPAND_REPLICAS + "] from value: [" + value + "] at index " + dash,
                e
            );
        }
        String sMax = value.substring(dash + 1);
        if (sMax.equals(ALL_NODES_VALUE)) {