Fix csv_query_approx_count once binary type coercion PR is merged

[andygrove]

Describe the bug

csv_query_approx_count fails due to an edge case exposed in #3222

The test fails with:

"Plan(\"Aggregations require unique expression names but the expression \\\"APPROXDISTINCT(#aggregate_test_100.c9)\\\" at position 0 and \\\"APPROXDISTINCT(CAST(#aggregate_test_100.c9 AS Utf8))\\\" at position 1 have the same name. Consider aliasing (\\\"AS\\\") one of them.\")

However, the expressions are already aliased. The alias is dropped before the error check above and this part of the codebase needs some reworking. It is not trivial to fix.

To Reproduce

#[tokio::test]
async fn csv_query_approx_count() -> Result<()> {
    let ctx = SessionContext::new();
    register_aggregate_csv(&ctx).await?;
    let sql = "SELECT approx_distinct(c9) count_c9, approx_distinct(cast(c9 as varchar)) count_c9_str FROM aggregate_test_100";
    let actual = execute_to_batches(&ctx, sql).await;
    let expected = vec![
        "+----------+--------------+",
        "| count_c9 | count_c9_str |",
        "+----------+--------------+",
        "| 100      | 99           |",
        "+----------+--------------+",
    ];
    assert_batches_eq!(expected, &actual);
    Ok(())
}

Expected behavior
Should pass

Additional context
None