### 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
private final ShardAllocationCounts primaries = new ShardAllocationCounts();
        private final ShardAllocationCounts replicas = new ShardAllocationCounts();
        private final Metadata clusterMetadata;
        ShardAllocationStatus(Metadata clusterMetadata) {
            this.clusterMetadata = clusterMetadata;
        }
        public void addPrimary(ShardRouting routing, ClusterState state, NodesShutdownMetadata shutdowns, boolean verbose) {
            primaries.increment(routing, state, shutdowns, verbose);
        }
        public void addReplica(ShardRouting routing, ClusterState state, NodesShutdownMetadata shutdowns, boolean verbose) {
            replicas.increment(routing, state, shutdowns, verbose);
        }
        public HealthStatus getStatus() {
            if (primaries.available == false) {
                return RED;
            } else if (replicas.available == false) {
                return YELLOW;
            } else {
                return GREEN;
            }
        }
        public String getSymptom() {
            var builder = new StringBuilder("This cluster has ");
            if (primaries.unassigned > 0
                || primaries.unassigned_new > 0
                || primaries.unassigned_restarting > 0
                || replicas.unassigned > 0