### 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
.settings(
                    Settings.builder()
                        .put("index.version.created", Version.CURRENT)
                        .put(DataTier.TIER_PREFERENCE_SETTING.getKey(), "data_warm")
                        .put(INDEX_ROUTING_REQUIRE_GROUP_SETTING.getKey() + "data", "warm")
                )
                .numberOfShards(numShards)
                .numberOfReplicas(numReplicas)
                .build();
            final IndexRoutingTable.Builder indexRountingTableBuilder = new IndexRoutingTable.Builder(indexMetadata.getIndex());
            for (int shardIdNumber = 0; shardIdNumber < numShards; shardIdNumber++) {
                ShardId shardId = new ShardId(indexMetadata.getIndex(), shardIdNumber);
                final IndexShardRoutingTable.Builder shardBuilder = new IndexShardRoutingTable.Builder(shardId);
                ShardRouting shardRouting = ShardRouting.newUnassigned(
                    shardId,
                    true,
                    RecoverySource.ExistingStoreRecoverySource.INSTANCE,
                    decidersNoUnassignedInfo
                );
                shardBuilder.addShard(shardRouting);
                if (shardIdNumber < numReplicas) {
                    shardBuilder.addShard(
                        ShardRouting.newUnassigned(
                            shardId,
                            false,
                            RecoverySource.EmptyStoreRecoverySource.INSTANCE,
                            decidersNoUnassignedInfo
                        )
                    );
                }