### Elasticsearch Version

8.9.0

### Installed Plugins

_No response_

### Java Version

_bundled_

### OS Version

any

### Problem Description

If the context text supplied to the Question Answering task is longer than the model's `max_sequence_length` and `truncate` is set to `none` then inference on the model fails with the message:

```
status_exception: question answering result has invalid dimension, expected 2 found [6] 
```
<img width="1438" alt="Screenshot 2023-07-25 at 08 21 37" src="https://github.com/elastic/elasticsearch/assets/2353640/12d296f6-03b2-4cda-89ce-7399348c4104">


### Steps to Reproduce

Use long input text to the question answering task


### Work Aroundf
The fix is to truncate the context which unfortunately may remove the part of the document containing the answer. For reference the call is documented here

```
POST _ml/trained_models/distilbert-base-cased-distilled-squad/deployment/_infer
{
  "docs":[{ "text_field": "question answering context"}],
  "inference_config": {
    "question_answering": {
      "question": "The question to ask",
      "tokenization": {
        "bert": {
          "truncate": "second",
          "span": -1          
        }
      }
    }
  }
}
````

x-pack/plugin/ml/src/main/java/org/elasticsearch/xpack/ml/inference/nlp/tokenizers/TokenizationResult.java
public static final int SPECIAL_TOKEN_POSITION = -1;
    private final List<String> vocab;
    private final List<Tokens> tokens;
    private final int maxLength;
    private final int padTokenId;
    protected TokenizationResult(List<String> vocab, List<Tokens> tokenizations, int padTokenId) {
        this.vocab = vocab;
        this.tokens = tokenizations;
        this.padTokenId = padTokenId;
        int max = 0;
        Set<Integer> sequenceIds = new HashSet<>();
        for (Tokens tokenization : tokenizations) {
            max = Math.max(tokenization.tokenIds.length, max);
            if (sequenceIds.contains(tokenization.sequenceId()) && tokenization.spanPrev == -1) {
                throw new IllegalArgumentException("cannot window a sequence without a configured span");
            }
            sequenceIds.add(tokenization.sequenceId);
        }
        this.maxLength = max;
    }
    public Map<Integer, List<Tokens>> getTokensBySequenceId() {
        return tokens.stream().collect(Collectors.groupingBy(Tokens::sequenceId));
    }