### Description

Elasticsearch defines the concept of a [feature](https://www.elastic.co/guide/en/elasticsearch/reference/current/get-features-api.html) for the purpose of better managing them when snapshotting/restoring them via the [feature_states field](https://www.elastic.co/guide/en/elasticsearch/reference/current/create-snapshot-api.html#create-snapshot-api-feature-states)

The `shards_availability` health indicator currently diagnoses the condition of indices needing to be [restored from a snapshot](https://github.com/elastic/elasticsearch/blob/main/server/src/main/java/org/elasticsearch/cluster/routing/allocation/ShardsAvailabilityHealthIndicatorService.java#L138) and recommends a [troubleshooting guide](http://ela.st/restore-snapshot)

However, since `8.x` the restore API **must** use `feature_states` instead of specifying systems indices or system data streams as part of the `indices` field.

This proposes the `affected_resources` for the `restore_from_snapshot` diagnosis return the indices that are not part of a `feature` under the `INDICES` type, and a new type `FEATURES`.
e.g. instead of current behaviour
```
"affected_resources": {
  "indices": [
    ".geoip_databases",
    "test_index"
    ]
}
```
we could return:
```
"affected_resources": {
  "indices": [
    "test_index"
   ], 
  "features": [
     "geoip"
  ]
}
```



server/src/main/java/org/elasticsearch/cluster/routing/allocation/ShardsAvailabilityHealthIndicatorService.java
* @return A list of diagnoses for the provided unassigned shard
     */
    List<Diagnosis.Definition> checkDataTierRelatedIssues(
        IndexMetadata indexMetadata,
        List<NodeAllocationResult> nodeAllocationResults,
        ClusterState clusterState
    ) {
        List<Diagnosis.Definition> diagnosisDefs = new ArrayList<>();
        if (indexMetadata.getTierPreference().size() > 0) {
            List<NodeAllocationResult> dataTierAllocationResults = nodeAllocationResults.stream()
                .filter(hasDeciderResult(DATA_TIER_ALLOCATION_DECIDER_NAME, Decision.Type.YES))
                .toList();
            if (dataTierAllocationResults.isEmpty()) {
                
                for (String tier : indexMetadata.getTierPreference()) {
                    Optional.ofNullable(ACTION_ENABLE_TIERS_LOOKUP.get(tier)).ifPresent(diagnosisDefs::add);
                }
            } else {
                
                Set<DiscoveryNode> dataTierNodes = dataTierAllocationResults.stream()
                    .map(NodeAllocationResult::getNode)
                    .collect(Collectors.toSet());
                
                Set<String> dataTierRolesAvailable = dataTierNodes.stream()
                    .map(DiscoveryNode::getRoles)
                    .flatMap(Set::stream)
                    .map(DiscoveryNodeRole::roleName)
                    .collect(Collectors.toSet());
                
                String preferredTier = indexMetadata.getTierPreference()