### 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_
server/src/main/java/org/elasticsearch/cluster/routing/allocation/DataTier.java
public static Settings getPreferredTiersConfigurationSettings(String targetTier) {
        final Settings res = PREFERENCE_TIER_CONFIGURATION_SETTINGS.get(targetTier);
        if (res == null) {
            throw new IllegalArgumentException("invalid data tier [" + targetTier + "]");
        }
        return res;
    }
    /**
     * Returns true iff the given settings have a data tier setting configured
     */
    public static boolean isExplicitDataTier(Settings settings) {
        /*
         * This method can be called before the o.e.n.NodeRoleSettings.NODE_ROLES_SETTING is
         * initialized. We do not want to trigger initialization prematurely because that will bake
         *  the default roles before plugins have had a chance to register them. Therefore,
         * to avoid initializing this setting prematurely, we avoid using the actual node roles
         * setting instance here in favor of the string.
         */
        if (settings.hasValue("node.roles")) {
            return settings.getAsList("node.roles").stream().anyMatch(DataTier::validTierName);
        }
        return false;
    }
    public static boolean isContentNode(DiscoveryNode discoveryNode) {
        return discoveryNode.getRoles().contains(DiscoveryNodeRole.DATA_CONTENT_NODE_ROLE)
            || discoveryNode.getRoles().contains(DiscoveryNodeRole.DATA_ROLE);
    }
    public static boolean isHotNode(DiscoveryNode discoveryNode) {
        return discoveryNode.getRoles().contains(DiscoveryNodeRole.DATA_HOT_NODE_ROLE)
            || discoveryNode.getRoles().contains(DiscoveryNodeRole.DATA_ROLE);