### Description

![image](https://github.com/elastic/elasticsearch/assets/76245/d0443170-0419-4759-b505-7620ff3d6594)

The execution time of grouping stats by multiple keywords has increased: 1.2 to 1.6 seconds (with doc_partitioning), 4.3 to 6.7 seconds (with shard_partitioning). The equivalent query with the _search API takes 1.8 seconds.

`from nyc_taxis | ... | stats c = count(dropoff_datetime) by trip_type, payment_type, vendor_id`

This regression occurred since July 2, 2023, and I suspect it may be due to the PR: [Support multivalued fields on arbitrary grouping](https://github.com/elastic/elasticsearch-internal/pull/1340).

/cc @nik9000
x-pack/plugin/esql/compute/src/test/java/org/elasticsearch/compute/operator/MultivalueDedupeTests.java
for (boolean nullAllowed : new boolean[] { false, true }) {
                for (int max : new int[] { 10, 100, 1000 }) {
                    params.add(new Object[] { elementType, 1000, nullAllowed, 1, max, 0, 0 });
                    params.add(new Object[] { elementType, 1000, nullAllowed, 1, max, 0, 100 });
                }
            }
        }
        return params;
    }
    private final ElementType elementType;
    private final int positionCount;
    private final boolean nullAllowed;
    private final int minValuesPerPosition;
    private final int maxValuesPerPosition;
    private final int minDupsPerPosition;
    private final int maxDupsPerPosition;
    public MultivalueDedupeTests(
        ElementType elementType,
        int positionCount,
        boolean nullAllowed,
        int minValuesPerPosition,
        int maxValuesPerPosition,
        int minDupsPerPosition,
        int maxDupsPerPosition
    ) {
        this.elementType = elementType;
        this.positionCount = positionCount;
        this.nullAllowed = nullAllowed;
        this.minValuesPerPosition = minValuesPerPosition;
        this.maxValuesPerPosition = maxValuesPerPosition;