### 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
import java.util.function.Predicate;
import java.util.stream.Collectors;
import java.util.stream.Stream;
import static java.util.stream.Collectors.joining;
import static org.elasticsearch.cluster.health.ClusterShardHealth.getInactivePrimaryHealth;
import static org.elasticsearch.cluster.metadata.IndexMetadata.INDEX_ROUTING_INCLUDE_GROUP_PREFIX;
import static org.elasticsearch.cluster.metadata.IndexMetadata.INDEX_ROUTING_INCLUDE_GROUP_SETTING;
import static org.elasticsearch.cluster.metadata.IndexMetadata.INDEX_ROUTING_REQUIRE_GROUP_PREFIX;
import static org.elasticsearch.cluster.metadata.IndexMetadata.INDEX_ROUTING_REQUIRE_GROUP_SETTING;
import static org.elasticsearch.cluster.routing.allocation.decider.EnableAllocationDecider.INDEX_ROUTING_ALLOCATION_ENABLE_SETTING;
import static org.elasticsearch.cluster.routing.allocation.decider.ShardsLimitAllocationDecider.CLUSTER_TOTAL_SHARDS_PER_NODE_SETTING;
import static org.elasticsearch.cluster.routing.allocation.decider.ShardsLimitAllocationDecider.INDEX_TOTAL_SHARDS_PER_NODE_SETTING;
import static org.elasticsearch.health.Diagnosis.Resource.Type.INDEX;
import static org.elasticsearch.health.HealthStatus.GREEN;
import static org.elasticsearch.health.HealthStatus.RED;
import static org.elasticsearch.health.HealthStatus.YELLOW;
import static org.elasticsearch.health.node.HealthIndicatorDisplayValues.getTruncatedIndices;
import static org.elasticsearch.health.node.HealthIndicatorDisplayValues.indicesComparatorByPriorityAndName;
/**
 * This indicator reports health for shards.
 * <p>
 * Indicator will report:
 * * RED when one or more primary shards are not available
 * * YELLOW when one or more replica shards are not available
 * * GREEN otherwise
 * <p>
 * Each shard needs to be available and replicated in order to guarantee high availability and prevent data loses.
 * Shards allocated on nodes scheduled for restart (using nodes shutdown API) will not degrade this indicator health.
 */
public class ShardsAvailabilityHealthIndicatorService implements HealthIndicatorService {