### 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"
  ]
}
```



benchmarks/src/main/java/org/elasticsearch/benchmark/routing/allocation/ShardsAvailabilityHealthIndicatorBenchmark.java
indexRountingTableBuilder.addIndexShard(shardBuilder);
            }
            routingTable.add(indexRountingTableBuilder);
            mb.put(indexMetadata, false);
        }
        ClusterState initialClusterState = ClusterState.builder(ClusterName.CLUSTER_NAME_SETTING.getDefault(Settings.EMPTY))
            .metadata(mb)
            .routingTable(routingTable)
            .nodes(nb)
            .build();
        Settings settings = Settings.builder().put("node.name", ShardsAvailabilityHealthIndicatorBenchmark.class.getSimpleName()).build();
        ThreadPool threadPool = new ThreadPool(settings);
        ClusterService clusterService = new ClusterService(
            Settings.EMPTY,
            new ClusterSettings(Settings.EMPTY, ClusterSettings.BUILT_IN_CLUSTER_SETTINGS),
            threadPool,
            new TaskManager(Settings.EMPTY, threadPool, Collections.emptySet())
        );
        clusterService.getClusterApplierService().setInitialState(initialClusterState);
        indicatorService = new ShardsAvailabilityHealthIndicatorService(clusterService, allocationService);
    }
    private int toInt(String v) {
        return Integer.parseInt(v.trim());
    }
    @Benchmark
    public HealthIndicatorResult measureCalculate() {
        return indicatorService.calculate(true, HealthInfo.EMPTY_HEALTH_INFO);
    }
}