[FEATURE] Support more than one retaining events `dedup` pushdown with Calcite

[LantaoJin]

Is your feature request related to a problem?
#3913 only support dedup pushdown when

1. number of retaining events no larger than 1
2. dedup field list only contain one field
3. the dedup field is one of field of index
4. the dedup field type is keyword (or contain keyword subfield) or numeric

For the cases not matched (1) and (2), we can support them by using inner_hits. But currently, the response parser cannot handle inner_hits from response.

What solution would you like?
A better response parser to handle inner_hits and new rule to handle the cases (1) and (2).

To support the case (1):

{
  "from": 0,
  "size": 10000,
  "timeout": "1m",
  "_source": false,
  "collapse": {
    "field": "gender.keyword",
    "inner_hits": {
      "name": "level_1",
      "size": 2,
      "_source": {
        "includes": [
          "account_number",
          "gender",
          "age"
        ],
        "excludes": []
      }
    }
  }
}

[penghuo]

Should we enhancement on OpenSearch collapse to support dedup command, e.g. multiple field dedup?

[LantaoJin]

Should we enhancement on OpenSearch collapse to support dedup command, e.g. multiple field dedup?

OpenSearch collapse cannot support multiple fields. But there is <1% dedup command with more than one field in F's usage.