### 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
max = Integer.MAX_VALUE;
        } else {
            try {
                max = Integer.parseInt(sMax);
            } catch (NumberFormatException e) {
                throw new IllegalArgumentException(
                    "failed to parse [" + IndexMetadata.SETTING_AUTO_EXPAND_REPLICAS + "] from value: [" + value + "] at index " + dash,
                    e
                );
            }
        }
        return new AutoExpandReplicas(min, max, true);
    }
    public AutoExpandReplicas {
        if (minReplicas > maxReplicas) {
            throw new IllegalArgumentException(
                "["
                    + IndexMetadata.SETTING_AUTO_EXPAND_REPLICAS
                    + "] minReplicas must be =< maxReplicas but wasn't "
                    + minReplicas
                    + " > "
                    + maxReplicas
            );
        }
    }
    int getMaxReplicas(int numDataNodes) {
        return Math.min(maxReplicas, numDataNodes - 1);
    }
    public boolean expandToAllNodes() {
        return maxReplicas == Integer.MAX_VALUE;