Fix opensearch query parser

[igniting]

Also specify schema for id in arxiv-titles-384-angular filters dataset. This is needed as default mapping created by opensearch takes the type as float, but in the dataset we also have string. This leads to 99% precision on the test dataset with opensearch.

{
  "params": {
    "dataset": "arxiv-titles-384-angular-filters",
    "experiment": "opensearch-default",
    "engine": "opensearch",
    "parallel": 10,
    "config": {
      "knn.algo_param.ef_search": 128
    }
  },
  "results": {
    "total_time": 391.3466711850051,
    "mean_time": 0.37053632343088827,
    "mean_precisions": 0.98962,
    "std_time": 0.3485163122349799,
    "min_time": 0.04950378900684882,
    "max_time": 3.548553360000369,
    "rps": 25.552791773390613,
    "p95_time": 1.0473700279486362,
    "p99_time": 1.4396829416653787
  }
}

Fixes #171

[igniting]

@KShivendu can you take a look?

[KShivendu]

Thanks. Will check soon.