[BUG] Enable support for default model id on HybridQueryBuilder

[vibrantvarun]

What is the bug?

When a neural query enricher processor is created to enable the support for default model id and the neural query clause present at inner level of hybrid search query then the processor cannot add the model id in the neural clause.

How can one reproduce the bug?

1. Create a Neural Query Enricher
2. Create a index and add the document
3. Create a search pipeline for (Normalization Processor)
4. Trigger hybrid query in the below shape

query{
     hybrid{
            queries[
                  neural {
                       // do not pass model id here as you expect that neural query enricher will add it here.
                  }
           ]  
     }
}

Sample query

{
  "from" : 0,
  "size" : 1000,
  "query": {
    "hybrid": {
      "queries": [
        {
          "match": {
            "passage": {
              "query": "how many camels are there in the world."
            }
          }
        },
        {
          "neural": {
            "content_vector": {
              "query_text": "how many camels are there in the world.",
              "k": 10,
              "filter" :
              {
                "bool" :
                {
                  "must": [
                    {
                      "term": {
                      "publisher_id": {
                        "value": "abc"
                        }
                      }
                    },
                    {
                      "term": {
                      "published": {
                        "value": true
                        }
                      }
                    }
                  ]
                }
              }
            }
          }
        }
      ]
    }
  },
  "_source": true
}

What is the expected behavior?

Neural Query Enricher processor should be able to add the model id at inner level of hybrid query clause.

Do you have any additional context?

The fix to the bug is
Override the visit method from Querybuilder interface in HybridQueryBuilder and define it to the way that it parses the inner list of query builders.

[vibrantvarun]

PR is merged now