Adds ef_search support for Lucene kNN queries

[shatejas]

Description

Lucene queries use k as efsearch. So we take the max of two to pass is the right k value to Lucene. The size parameter will dictate the number of the hits

curl -XGET "http://localhost:9200/lucene-hnsw-index/_search" -H 'Content-Type: application/json' -d'
{
"size": 1,
  "query": {
    "knn": {
      "lucene_vector": {
        "vector": [2.5, 3.5, 2.2],
        "k": 3,
        "method_parameters": {
          "ef_search": 5
        }
        }
      }
    }
  }'

{
  "took": 4,
  "timed_out": false,
  "_shards": {
    "total": 1,
    "successful": 1,
    "skipped": 0,
    "failed": 0
  },
  "hits": {
    "total": {
      "value": 4,
      "relation": "eq"
    },
    "max_score": 1,
    "hits": [
      {
        "_index": "lucene-hnsw-index",
        "_id": "2",
        "_score": 1,
        "_source": {
          "lucene_vector": [
            2.5,
            3.5,
            2.2
          ],
          "price": 7.1
        }
      }
    ]
  }
}

Issues Resolved

#1537

Check List

• New functionality includes testing.
  • All tests pass
• Commits are signed as per the DCO using --signoff

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[naveentatikonda]

Why are we removing this ?

[shatejas]

It was a leftover from this PR https://github.com/opensearch-project/k-NN/pull/1742/files. The import is not needed. Sorry for the confusion

[naveentatikonda]

Can you add a function to create the query as it is duplicated multiple times

[shatejas]

It has a different request everytime. The create request itself is using a builder so wrapping it up with a function is moot

[junqiu-lei]

For the end to end test, can we use XContentBuilder to build the query?

https://github.com/opensearch-project/k-NN/blob/main/src/testFixtures/java/org/opensearch/knn/KNNRestTestCase.java#L213

[shatejas]

Its much more convenient to use KNNBuilder. It converts to XContent underneath.

Not opposed to it but any specific reason we should move to xcontent for happy case tests?

[junqiu-lei]

Using XContentBuilder can better mock end-user API calls by simulating JSON content creation and ensuring end-to-end functionality.

KNNBuilder is an internal method, and relying on it in integration test has the possibility to lead to fragile tests that may break with internal changes, even if the public API remains stable.

[shatejas]

Fair, will change it