### 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/main/java/org/elasticsearch/xpack/cluster/metadata/MetadataMigrateToDataTiersRoutingService.java
Map<String, LifecycleAction> actionMap = new HashMap<>(phase.getActions());
                
                
                if (allocateAction.getNumberOfReplicas() != null || allocateAction.getTotalShardsPerNode() != null) {
                    
                    AllocateAction updatedAllocateAction = new AllocateAction(
                        allocateAction.getNumberOfReplicas(),
                        allocateAction.getTotalShardsPerNode(),
                        null,
                        null,
                        null
                    );
                    actionMap.put(allocateAction.getWriteableName(), updatedAllocateAction);
                    logger.debug(
                        "ILM policy [{}], phase [{}]: updated the allocate action to [{}]",
                        lifecyclePolicy.getName(),
                        phase.getName(),
                        allocateAction
                    );
                } else {
                    
                    actionMap.remove(allocateAction.getWriteableName());
                    logger.debug("ILM policy [{}], phase [{}]: removed the allocate action", lifecyclePolicy.getName(), phase.getName());
                }
                
                
                if (actionMap.containsKey(MigrateAction.NAME)) {
                    MigrateAction migrateAction = (MigrateAction) actionMap.get(MigrateAction.NAME);
                    if (migrateAction.isEnabled() == false) {
                        actionMap.remove(MigrateAction.NAME);