### Elasticsearch Version

8.8.2

### Installed Plugins

_No response_

### Java Version

_bundled_

### OS Version

Mac OS X

### Problem Description

Under certain conditions, fetching a particular field value using the "fields" API can lead to `string_index_out_of_bounds_exception`.
The queried field needs to be inside a "nested" object and in addition to the field name, all fields need to be queries as well (`*`).
Both fields requested also need to be requested with `"include_unmapped": true`. 

### Steps to Reproduce

```
DELETE testindex

PUT testindex
{
    "mappings": {
        "dynamic": "false",
        "properties": {
            "nested_field": {
                "type": "nested",
                "properties": {
                    "file": {
                        "type": "keyword"
                    }
                }
            }
        }
    }
}

POST testindex/_doc
{
    "nested_field": {        
            "file": "somefile.txt"
    }
}

GET testindex/_search
{
  "_source": false,
  "fields": [
    {
      "field": "file",
      "include_unmapped": true
    },
    {
      "field": "*",
      "include_unmapped": true
    }
  ],
  "query": {
    "match_all" : {}
  }
}
```

This gives the following error:
```
{
    "error": {
        [...],
        "caused_by": {
            "type": "string_index_out_of_bounds_exception",
            "reason": "Range [13, 4) out of bounds for length 4",
            "caused_by": {
                "type": "string_index_out_of_bounds_exception",
                "reason": "Range [13, 4) out of bounds for length 4"
            }
        }
    },
    "status": 500
}
```

### Logs (if relevant)

_No response_
server/src/main/java/org/elasticsearch/search/fetch/subphase/UnmappedFieldFetcher.java
*/
    public UnmappedFieldFetcher(Set<String> mappedFields, List<String> unmappedFetchPatterns) {
        List<String> unmappedWildcardPatterns = new ArrayList<>();
        
        
        for (String pattern : unmappedFetchPatterns) {
            if (Regex.isSimpleMatchPattern(pattern)) {
                unmappedWildcardPatterns.add(pattern);
            } else {
                unmappedConcreteFields.add(pattern);
            }
        }
        this.unmappedFieldsFetchAutomaton = buildAutomaton(unmappedWildcardPatterns);
        this.mappedFields = mappedFields;
    }
    private static CharacterRunAutomaton buildAutomaton(List<String> patterns) {
        if (patterns.isEmpty()) {
            return null;
        }
        return new CharacterRunAutomaton(Regex.simpleMatchToAutomaton(patterns.toArray(String[]::new)), AUTOMATON_MAX_DETERMINIZED_STATES);
    }
    /**
     * Collect unmapped fields from a Source
     * @param documentFields    a map to receive unmapped field values as DocumentFields
     * @param source            the Source
     */
    public void collectUnmapped(Map<String, DocumentField> documentFields, Source source) {
        if (this.unmappedFieldsFetchAutomaton == null && this.unmappedConcreteFields.isEmpty()) {
            return;
        }