[BUG] sort queries on half_float data type is failing

[gashutos]

Describe the bug
As a part of this PR #8168, we introduced sort optimization (BKD point based) for all custom comparators.
But this seems didnt work well for half_float. half_float indexes with 2 bytes https://github.com/apache/lucene/blob/main/lucene/sandbox/src/java/org/apache/lucene/sandbox/document/HalfFloatPoint.java#L61. But during sort, we use FloatValuesSourceComparator https://github.com/gashutos/OpenSearch/blob/main/server/src/main/java/org/opensearch/index/fielddata/fieldcomparator/FloatValuesComparatorSource.java which uses FloatComparator. FloatComparator tries to go with 4 bytesize and hence, sort query on half_float fails with below error.

"reason": "Field price is indexed with 2 bytes per dimension, but org.opensearch.index.fielddata.fieldcomparator.FloatValuesComparatorSource$1@37f62528 expected 4"

To Reproduce
Create a Index with the following mapping -

PUT test-float
{
  "mappings": {
    "properties": {
      "price":{
        "type": "half_float"
      }
    }
  }
}

Ingest a sample document which is in the valid range as per the documentation -

PUT test-float/_doc/1
{
  "price":3.31
}

Now try to search and perform the below query -

GET test-float/_search
{
  "sort": [
    {
      "price": {
        "order": "desc"
      }
    }
  ]
}

The following error would be visible for the domain with the latest patch -

"failures": [
      {
        "shard": 4,
        "index": "test-float",
        "node": "H9uPpq8XQnukyqCmkr_vPw",
        "reason": {
          "type": "illegal_argument_exception",
          "reason": "Field price is indexed with 2 bytes per dimension, but org.opensearch.index.fielddata.fieldcomparator.FloatValuesComparatorSource$1@37f62528 expected 4"
        }
      }
    ]

=====
Complete Output -
=====

{
  "took": 7,
  "timed_out": false,
  "_shards": {
    "total": 5,
    "successful": 4,
    "skipped": 0,
    "failed": 1,
    "failures": [
      {
        "shard": 4,
        "index": "test-float",
        "node": "H9uPpq8XQnukyqCmkr_vPw",
        "reason": {
          "type": "illegal_argument_exception",
          "reason": "Field price is indexed with 2 bytes per dimension, but org.opensearch.index.fielddata.fieldcomparator.FloatValuesComparatorSource$1@37f62528 expected 4"
        }
      }
    ]
  },
  "hits": {
    "total": {
      "value": 0,
      "relation": "eq"
    },
    "max_score": null,
    "hits": []
  }
}