[FEATURE] Support push down Sort/Filter into TableScanBuilder through Project

[qianheng-aws]

Is your feature request related to a problem?
Sort or Filter cannot be pushed down into TableScan due to Project.

POST _plugins/_ppl/_explain
{
  "query": """
    source=opensearch_dashboards_sample_data_flights | fields FlightTimeMin |where FlightTimeMin > 0  |  sort FlightTimeMin 
  """
}

# response

{
  "root": {
    "name": "ProjectOperator",
    "description": {
      "fields": "[FlightTimeMin]"
    },
    "children": [
      {
        "name": "SortOperator",
        "description": {
          "sortList": {
            "FlightTimeMin": {
              "sortOrder": "ASC",
              "nullOrder": "NULL_FIRST"
            }
          }
        },
        "children": [
          {
            "name": "FilterOperator",
            "description": {
              "conditions": ">(FlightTimeMin, 0)"
            },
            "children": [
              {
                "name": "ProjectOperator",
                "description": {
                  "fields": "[FlightTimeMin]"
                },
                "children": [
                  {
                    "name": "OpenSearchIndexScan",
                    "description": {
                      "request": """OpenSearchQueryRequest(indexName=opensearch_dashboards_sample_data_flights, sourceBuilder={"from":0,"size":200,"timeout":"1m","_source":{"includes":["FlightTimeMin"],"excludes":[]}}, searchDone=false)"""
                    },
                    "children": []
                  }
                ]
              }
            ]
          }
        ]
      }
    ]
  }
}

What solution would you like?
Option1: remove ProjectOperator after pushed it down into TableScan. Not clear of the background why we intentionally wants to keep it here.

sql/opensearch/src/main/java/org/opensearch/sql/opensearch/storage/scan/OpenSearchIndexScanQueryBuilder.java

Lines 79 to 83 in 14a80a9

	public boolean pushDownProject(LogicalProject project) {
	requestBuilder.pushDownProjects(findReferenceExpressions(project.getProjectList()));
	// Return false intentionally to keep the original project operator
	return false;

Option2: support push down Sort/Filter under Project.

What alternatives have you considered?

Do you have any additional context?
Add any other context or screenshots about the feature request here.

[dblock]

[Catch All Triage - 1, 2, 3, 4, 5]