Output schema of the CopyTo logical plan is not correct.

[bert-beyondloops]

Describe the bug

The output schema of the CopyTo logical plan currently directly outputs the underlying schema of it's child.
The physical plan however always returns a 1 row/column count which represents the number of affected rows.

This is inconsistent.

To Reproduce

Following test fails :

#[tokio::test]
async fn test_copy_schema() -> Result<()> {
    let tmp_dir = TempDir::new()?;

    let session_state = SessionStateBuilder::new_with_default_features().build();

    let session_ctx = SessionContext::new_with_state(session_state);

    let schema = Arc::new(Schema::new(vec![Field::new("a", DataType::Int64, true)]));

    // Create and register the source table with the provided schema and data
    let source_table = Arc::new(MemTable::try_new(schema.clone(), vec![vec![]])?);
    session_ctx.register_table("source_table", source_table.clone())?;

    let target_path = tmp_dir.path().join("target.csv");

    let query = format!(
        "COPY source_table TO '{:?}' STORED AS csv",
        target_path.to_str().unwrap()
    );

    let result = session_ctx.sql(&query).await?;
    assert_logical_expr_schema_eq_physical_expr_schema(result).await?;
    Ok(())
}

The schema of the physical output is not the same as the logical plan.

Expected behavior

The CopyTo logical plan returns the same schema as the physical plan, being a 1 column named "count"

Additional context

No response