### Elasticsearch Version

7.17, 8.x

### Installed Plugins

_No response_

### Java Version

_bundled_

### OS Version

Darwin

### Problem Description

The migrate to data tiers API can sometimes configure an illegal value for the `_tier_preference` setting for partially mounted indices.
This can happen if two conditions are met: 
1. if the partially mounted index doesn't have a `_tier_preference` configured
2. if the migrate to data tiers API doesn't perform any migration for this index (e.g. say this partially mounted index doesn't use the `data` custom attribute name for any allocation filtering, but either uses some other node attribute name or none at all)

In this case this piece of code kicks in to configure a default tier preference https://github.com/elastic/elasticsearch/blob/main/x-pack/plugin/ilm/src/main/java/org/elasticsearch/xpack/cluster/metadata/MetadataMigrateToDataTiersRoutingService.java#L534

This is wrong, and we should configure the `MountSearchableSnapshotRequest.Storage.defaultDataTiersPreference` as the tier preference.

Relates to https://github.com/elastic/elasticsearch/issues/84758

### Steps to Reproduce

1. Mount an index - `partial-test`
2. Remove the `_tier_preference` using
```
PUT partial-test/_settings
{
  "index.routing.allocation.include._tier_preference": null
}
```
3. Call the migrate to data tiers routing API 
```
POST /_ilm/migrate_to_data_tiers
```

### Logs (if relevant)

_No response_
x-pack/plugin/ilm/src/test/java/org/elasticsearch/xpack/cluster/metadata/MetadataMigrateToDataTiersRoutingServiceTests.java
null,
            false
        );
        assertThat(migratedEntitiesTuple.v2().removedIndexTemplateName, nullValue());
        
        assertThat(migratedEntitiesTuple.v1().metadata().templatesV2().get(composableTemplateName), is(notNullValue()));
    }
    public void testMigrationSetsEnforceTierPreferenceToTrue() {
        ClusterState clusterState;
        Tuple<ClusterState, MigratedEntities> migratedEntitiesTuple;
        Metadata.Builder metadata;
        
        clusterState = ClusterState.builder(ClusterName.DEFAULT).build();
        migratedEntitiesTuple = migrateToDataTiersRouting(clusterState, null, null, REGISTRY, client, null, false);
        assertTrue(DataTier.ENFORCE_DEFAULT_TIER_PREFERENCE_SETTING.get(migratedEntitiesTuple.v1().metadata().persistentSettings()));
        assertFalse(migratedEntitiesTuple.v1().metadata().transientSettings().keySet().contains(DataTier.ENFORCE_DEFAULT_TIER_PREFERENCE));
        
        
        metadata = Metadata.builder();
        metadata.persistentSettings(Settings.builder().put(ENFORCE_DEFAULT_TIER_PREFERENCE, randomBoolean()).build());
        metadata.transientSettings(Settings.builder().put(ENFORCE_DEFAULT_TIER_PREFERENCE, randomBoolean()).build());
        clusterState = ClusterState.builder(ClusterName.DEFAULT).metadata(metadata).build();
        migratedEntitiesTuple = migrateToDataTiersRouting(clusterState, null, null, REGISTRY, client, null, false);
        assertTrue(DataTier.ENFORCE_DEFAULT_TIER_PREFERENCE_SETTING.get(migratedEntitiesTuple.v1().metadata().persistentSettings()));
        assertFalse(migratedEntitiesTuple.v1().metadata().transientSettings().keySet().contains(DataTier.ENFORCE_DEFAULT_TIER_PREFERENCE));
    }
    private LifecyclePolicyMetadata getWarmColdPolicyMeta(
        SetPriorityAction setPriorityAction,
        ShrinkAction shrinkAction,
        AllocateAction warmAllocateAction,