### 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
final String[] params = indicesShardsReplicasNodes.split("\\|");
        int numIndices = toInt(params[0]);
        int numShards = toInt(params[1]);
        int numReplicas = toInt(params[2]);
        int numNodes = toInt(params[3]);
        AllocationService allocationService = Allocators.createAllocationService(Settings.EMPTY);
        Metadata.Builder mb = Metadata.builder();
        RoutingTable.Builder rb = RoutingTable.builder();
        DiscoveryNodes.Builder nb = DiscoveryNodes.builder();
        Set<String> failedNodeIds = new HashSet<>();
        for (int i = 1; i <= numNodes; i++) {
            String nodeId = "node" + i;
            nb.add(Allocators.newNode(nodeId, Map.of()));
            failedNodeIds.add(nodeId);
        }
        UnassignedInfo decidersNoUnassignedInfo = new UnassignedInfo(
            UnassignedInfo.Reason.ALLOCATION_FAILED,
            null,
            null,
            failedNodeIds.size(),
            System.nanoTime(),
            System.currentTimeMillis(),
            false,
            UnassignedInfo.AllocationStatus.DECIDERS_NO,
            failedNodeIds,
            null
        );
        RoutingTable.Builder routingTable = RoutingTable.builder();
        for (int i = 1; i <= numIndices; i++) {
            IndexMetadata indexMetadata = IndexMetadata.builder("test_" + i)