[FEATURE] Support Boosting for Neural Query

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A clear and concise description of what the problem is, e.g. I'm always frustrated when [...].
Currently, when using semantic search I have an issue where it perform poorly over exact keyword search with boosting for situations where I would like to artificially boost certain indices due to businees goals.

Sample Output:

{
  "took": 29,
  "timed_out": false,
  "_shards": {
    "total": 2,
    "successful": 2,
    "skipped": 0,
    "failed": 0
  },
  "hits": {
    "total": {
      "value": 28,
      "relation": "eq"
    },
    "max_score": 0.66891545,
    "hits": [
      {
        "_index": "A",
        "_id": "A-hjHkg4JVoxyrjVaY1T1fC",
        "_score": 0.66891545,
      },
      {
        "_index": "A",
        "_id": "A-4IIkZsGqs6AAGNJBPxFG2q",
        "_score": 0.66891545,
      },
      {
        "_index": "A",
        "_id": "A-PrFcKYXMGHTF6DSZ15zxw",
        "_score": 0.6600258,
      },
      {
        "_index": "B",
        "_id": "B-ppZ_YYBf08C9I8emn4W",
        "_score": 0.6593717,
      },
      {
        "_index": "A",
        "_id": "A-55mffVK1TqNteVpb6mri5d",
        "_score": 0.659091,
      }
    ]
  }
}

In this scenario I would like to apply a constant boost of 0.1 to the _score of index B .
I tried doing it within the Java Client like so:

NeuralQuery neuralQuery = new NeuralQuery.Builder()
                    .field(...)
                    .queryText(...)
                    .modelId(MODEL_ID)
                    .k(KNN_TOP_K)
                    .build();
            Query query = new Query.Builder()
                    .neural(neuralQuery)
                    .build();
            List<Map<String, Double>> indicesToBoost = List.of(Map.of(
                    "B", 0.1
            ));

            var searchResponse = openSearchJavaClient.search(
                    s -> s.index(UniversalSearchCategory.SEMANTIC_OFFERS.getIndexName())
                            .from(param.getOffset())
                            .size(param.getLimit())
                            .sort(sortOptions)
                            .query(query)
                            .source(sourceConfig)
                            .indicesBoost(indicesToBoost)
                    , Object.class
            );

But the scores do not get boosted at all.

What solution would you like?

A clear and concise description of what you want to happen.
I would like to see the score of the index B increase by 0.1.

{
        "_index": "B",
        "_id": "B-ppZ_YYBf08C9I8emn4W",
        "_score": 0.7593717,
}

What alternatives have you considered?

A clear and concise description of any alternative solutions or features you've considered.

Do you have any additional context?

Add any other context or screenshots about the feature request here.

Start by tracing the Java client's NeuralQuery, Query, and search request handling, including the indicesBoost option shown in the issue. Determine how boosting is expected to affect neural-query scores, then verify that an index B result receives the requested 0.1 increase in a representative search response.