Adding agg_for_doc_count even if distinct count is present in query

[expani]

Description

we are missing this check in SQL plugin causing agg_for_doc_count to be not added as an aggregate when Distinct Cardinality Aggregate is part of the query.

Adding this the plan's look like follows

[INFO ][o.o.s.o.r.OpenSearchQueryRequest] [runTask-0] Calcite Logical Plan after Conversion
 LogicalSystemLimit(sort0=[$0], dir0=[DESC-nulls-last], fetch=[10000], type=[QUERY_SIZE_LIMIT])
  LogicalSort(sort0=[$0], dir0=[DESC-nulls-last], fetch=[10])
    LogicalProject(u=[$1], RegionID=[$0], agg_for_doc_count=[$2])
      LogicalAggregate(group=[{0}], u=[APPROX_COUNT_DISTINCT($1)], agg_for_doc_count=[COUNT()])
        LogicalProject(RegionID=[$68], UserID=[$84])
          CalciteLogicalIndexScan(table=[[OpenSearch, hits]])

doc_count is expected for all scenarios.

This is required for merging at Coordinator to work properly. See https://github.com/opensearch-project/OpenSearch/blob/main/server/src/main/java/org/opensearch/search/aggregations/bucket/terms/InternalTerms.java#L395

There are multiple places that rely on doc count for instance https://github.com/opensearch-project/OpenSearch/blob/main/server/src/main/java/org/opensearch/search/aggregations/bucket/terms/InternalTerms.java#L474 relies on the same to prune buckets lower that a certain doc count.

More context in opensearch-project/OpenSearch#20263