Handling of Aggregates with multiple groupings sets is incorrect

[vbarua]

Describe the bug

In the presences of multiple grouping sets, the output schema for a AggregateRel consists of:

1. All expressions in the groupingExpressions field
2. All measures
3. An extra i32 column to indicate which grouping a row belongs to.

In Datafusion, the default order of the schema seems to be

1. All expressions in the groupingExpressions field
2. An extra i32 column to indicate which grouping a row belongs to.
3. All measures

This different in schemas does not appear to be handled in the consumer.

To Reproduce

The following Substrait plan

{
  "extensionUris": [
    {
      "extensionUriAnchor": 1,
      "uri": "https://github.com/substrait-io/substrait/blob/main/extensions/functions_arithmetic.yaml"
    }
  ],
  "extensions": [
    {
      "extensionFunction": {
        "extensionUriReference": 1,
        "functionAnchor": 1,
        "name": "sum:i8"
      }
    }
  ],
  "relations": [
    {
      "root": {
        "input": {
          "aggregate": {
            "common": {
              "emit": {
                "outputMapping": [
                  0, 1, 2
                ]
              }
            },
            "input": {
              "read": {
                "baseSchema": {
                  "names": [
                    "c0",
                    "c1"
                  ],
                  "struct": {
                    "nullability": "NULLABILITY_REQUIRED",
                    "types": [
                      {
                        "i8": {
                          "nullability": "NULLABILITY_NULLABLE"
                        }
                      },
                      {
                        "i8": {
                          "nullability": "NULLABILITY_NULLABLE"
                        }
                      }
                    ]
                  }
                },
                "common": {
                  "direct": {}
                },
                "virtualTable": {}
              }
            },
            "groupingExpressions": [
              {
                "selection": {
                  "directReference": {
                    "structField": {}
                  },
                  "rootReference": {}
                }
              },
              {
                "selection": {
                  "directReference": {
                    "structField": {
                      "field": 1
                    }
                  },
                  "rootReference": {}
                }
              }
            ],
            "groupings": [
              {
                "expressionReferences": [0]
              },
              {
                "expressionReferences": [1]
              },
              {
                "expressionReferences": [0, 1]
              }
            ],
            "measures": [
              {
                "measure": {
                  "arguments": [
                    {
                      "value": {
                        "selection": {
                          "directReference": {
                            "structField": {}
                          },
                          "rootReference": {}
                        }
                      }
                    }
                  ],
                  "functionReference": 1,
                  "invocation": "AGGREGATION_INVOCATION_ALL",
                  "outputType": {
                    "i8": {
                      "nullability": "NULLABILITY_NULLABLE"
                    }
                  },
                  "phase": "AGGREGATION_PHASE_INITIAL_TO_RESULT"
                }
              }
            ]
          }
        },
        "names": [
          "c0",
          "c1",
          "summation"
        ]
      }
    }
  ],
  "version": {
    "minorNumber": 29
  }
}

which captures a query like

SELECT c0, c1, sum(0) AS summation
FROM <some table>
GROUP BY GROUPING SETS((c0), (c1), (c0, c1))

yields the following DataFusion plan

Projection: c0, c1, __grouping_id AS summation
  Aggregate: groupBy=[[GROUPING SETS ((c0), (c1), (c0, c1))]], aggr=[[sum(c0)]]
    EmptyRelation: rows=0

With this plan, output column 2 should correspond to the summation, but in the Datafusion plan it is the __grouping_id column.

Expected behavior

We would expect something like instead

Projection: c0, c1, sum(c0) AS summation
  Aggregate: groupBy=[[GROUPING SETS ((c0), (c1), (c0, c1))]], aggr=[[sum(c0)]]
    EmptyRelation: rows=0

Additional context

I suspect that fixing this in the consumer will also reveal bugs in the producer around handling for multiple groupings sets.