### 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
case 0 -> Stream.empty();
                case 1 -> Stream.of("1 " + singular);
                default -> Stream.of(count + " " + plural);
            };
        }
        public HealthIndicatorDetails getDetails(boolean verbose) {
            if (verbose) {
                return new SimpleHealthIndicatorDetails(
                    Map.of(
                        "unassigned_primaries",
                        primaries.unassigned,
                        "initializing_primaries",
                        primaries.initializing,
                        "creating_primaries",
                        primaries.unassigned_new,
                        "restarting_primaries",
                        primaries.unassigned_restarting,
                        "started_primaries",
                        primaries.started + primaries.relocating,
                        "unassigned_replicas",
                        replicas.unassigned,
                        "initializing_replicas",
                        replicas.initializing,
                        "restarting_replicas",
                        replicas.unassigned_restarting,
                        "started_replicas",
                        replicas.started + replicas.relocating
                    )
                );
            } else {