### 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/node/Node.java
throw new IllegalStateException("Call close() first");
        }
        ThreadPool threadPool = injector.getInstance(ThreadPool.class);
        final boolean terminated = ThreadPool.terminate(threadPool, timeout, timeUnit);
        if (terminated) {
            
            
            if (nodeService.awaitClose(0, TimeUnit.MILLISECONDS) == false) {
                throw new IllegalStateException(
                    "Some shards are still open after the threadpool terminated. "
                        + "Something is leaking index readers or store references."
                );
            }
        }
        return terminated;
    }
    /**
     * Returns {@code true} if the node is closed.
     */
    public boolean isClosed() {
        return lifecycle.closed();
    }
    public Injector injector() {
        return this.injector;
    }
    /**
     * Hook for validating the node after network
     * services are started but before the cluster service is started
     * and before the network service starts accepting incoming network