### Elasticsearch Version

8.4, 8.5, 8.6

### Installed Plugins

_No response_

### Java Version

_bundled_

### OS Version

Darwin

### Problem Description

The shards availability indicator should always be reporting diagnosis when its status is RED/YELLOW.
However, when an index is on a data node that runs out of disk space it will report RED but no diagnosis.

### Steps to Reproduce

Have multi-node cluster where a data (non-master) node that hosts an index runs out of disk space (the index cannot relocate somewhere else).
Call the Health API and the output will be something along these lines:
```
    "shards_availability": {
      "status": "red",
      "symptom": "This cluster has all shards available.",
      "details": {
        "initializing_primaries": 1,
        "started_replicas": 0,
        "initializing_replicas": 0,
        "unassigned_primaries": 0,
        "started_primaries": 1,
        "creating_primaries": 0,
        "unassigned_replicas": 0,
        "restarting_primaries": 0,
        "restarting_replicas": 0
      },
      "impacts": [
        {
          "id": "elasticsearch:health:shards_availability:impact:primary_unassigned",
          "severity": 1,
          "description": "Cannot add data to 1 index [test_index]. Searches might return incomplete results.",
          "impact_areas": [
            "ingest",
            "search"
          ]
        }
      ] 
    }
``` 

### Logs (if relevant)

_No response_
server/src/main/java/org/elasticsearch/cluster/routing/allocation/ShardsAvailabilityHealthIndicatorService.java
|| replicas.unassigned_restarting > 0) {
                builder.append(
                    Stream.of(
                        createMessage(primaries.unassigned, "unavailable primary shard", "unavailable primary shards"),
                        createMessage(primaries.unassigned_new, "creating primary shard", "creating primary shards"),
                        createMessage(primaries.unassigned_restarting, "restarting primary shard", "restarting primary shards"),
                        createMessage(replicas.unassigned, "unavailable replica shard", "unavailable replica shards"),
                        createMessage(replicas.unassigned_restarting, "restarting replica shard", "restarting replica shards")
                    ).flatMap(Function.identity()).collect(joining(", "))
                ).append(".");
            } else {
                builder.append("all shards available.");
            }
            return builder.toString();
        }
        private static Stream<String> createMessage(int count, String singular, String plural) {
            return switch (count) {
                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,