### 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/test/java/org/elasticsearch/cluster/routing/allocation/ShardsAvailabilityHealthIndicatorServiceTests.java
List.of(
                new SystemIndices.Feature(
                    "feature-with-system-index",
                    "testing",
                    List.of(new SystemIndexDescriptor(standaloneSystemIndexPattern, "feature with index"))
                ),
                new SystemIndices.Feature(
                    "feature-with-system-data-stream",
                    "feature with data stream",
                    List.of(),
                    List.of(
                        new SystemDataStreamDescriptor(
                            featureDataStreamName,
                            "description",
                            SystemDataStreamDescriptor.Type.EXTERNAL,
                            new ComposableIndexTemplate(
                                List.of(systemDataStreamPattern),
                                null,
                                null,
                                null,
                                null,
                                null,
                                new ComposableIndexTemplate.DataStreamTemplate()
                            ),
                            Map.of(),
                            List.of("test"),
                            new ExecutorNames(
                                ThreadPool.Names.SYSTEM_CRITICAL_READ,
                                ThreadPool.Names.SYSTEM_READ,
                                ThreadPool.Names.SYSTEM_WRITE