### 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/test/java/org/elasticsearch/cluster/routing/allocation/ShardsAvailabilityHealthIndicatorServiceTests.java
Index index = indexMetadata.getIndex();
        
        DiscoveryNode hotNode = new DiscoveryNode(
            randomNodeId(),
            buildNewFakeTransportAddress(),
            Map.of(),
            Set.of(DiscoveryNodeRole.DATA_HOT_NODE_ROLE),
            Version.CURRENT
        );
        var clusterState = createClusterStateWith(
            List.of(indexMetadata),
            List.of(
                IndexRoutingTable.builder(index)
                    
                    .addShard(createShardRouting(new ShardId(index, 0), true, new ShardAllocation(hotNode.getId(), AVAILABLE)))
                    
                    .addShard(
                        createShardRouting(new ShardId(index, 1), true, new ShardAllocation(randomNodeId(), UNAVAILABLE, decidersNo()))
                    )
                    .build()
            ),
            List.of(),
            List.of(hotNode)
        );
        var service = createShardsAvailabilityIndicatorService();
        
        List<Diagnosis.Definition> actions = service.checkDataTierRelatedIssues(
            indexMetadata,
            List.of(
                new NodeAllocationResult(