### 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
public void testParseSettings() {
        AutoExpandReplicas autoExpandReplicas = AutoExpandReplicas.SETTING.get(
            Settings.builder().put("index.auto_expand_replicas", "0-5").build()
        );
        assertEquals(0, autoExpandReplicas.minReplicas());
        assertEquals(5, autoExpandReplicas.getMaxReplicas(8));
        assertEquals(2, autoExpandReplicas.getMaxReplicas(3));
        assertFalse(autoExpandReplicas.expandToAllNodes());
        autoExpandReplicas = AutoExpandReplicas.SETTING.get(Settings.builder().put("index.auto_expand_replicas", "0-all").build());
        assertEquals(0, autoExpandReplicas.minReplicas());
        assertEquals(5, autoExpandReplicas.getMaxReplicas(6));
        assertEquals(2, autoExpandReplicas.getMaxReplicas(3));
        assertTrue(autoExpandReplicas.expandToAllNodes());
        autoExpandReplicas = AutoExpandReplicas.SETTING.get(Settings.builder().put("index.auto_expand_replicas", "1-all").build());
        assertEquals(1, autoExpandReplicas.minReplicas());
        assertEquals(5, autoExpandReplicas.getMaxReplicas(6));
        assertEquals(2, autoExpandReplicas.getMaxReplicas(3));
        assertTrue(autoExpandReplicas.expandToAllNodes());
    }
    public void testInvalidValues() {
        try {
            AutoExpandReplicas.SETTING.get(Settings.builder().put("index.auto_expand_replicas", "boom").build());
            fail();
        } catch (IllegalArgumentException ex) {
            assertEquals("failed to parse [index.auto_expand_replicas] from value: [boom] at index -1", ex.getMessage());