Add sql_parser.default_null_ordering config option to customize the default null ordering

[goldmedal]

Which issue does this PR close?

• Closes #.

Rationale for this change

The default null ordering is much different in different database.
In Postgres, the null value is considered as the max value.

psql=# select * from (values (1, 'one'), (2, 'two'), (null, 'three')) t(c1, c2) order by c1 asc;
 c1 |  c2   
----+-------
  1 | one
  2 | two
    | three
(3 rows)

psql=# select * from (values (1, 'one'), (2, 'two'), (null, 'three')) t(c1, c2) order by c1 desc;
 c1 |  c2   
----+-------
    | three
  2 | two
  1 | one
(3 rows)

In DuckDB, the null value is always at the last

D select * from (values (1, 'one'), (2, 'two'), (null, 'three')) t(c1, c2) order by c1 asc;
┌───────┬─────────┐
│  c1   │   c2    │
│ int32 │ varchar │
├───────┼─────────┤
│     1 │ one     │
│     2 │ two     │
│  NULL │ three   │
└───────┴─────────┘
D select * from (values (1, 'one'), (2, 'two'), (null, 'three')) t(c1, c2) order by c1 desc;
┌───────┬─────────┐
│  c1   │   c2    │
│ int32 │ varchar │
├───────┼─────────┤
│     2 │ two     │
│     1 │ one     │
│  NULL │ three   │
└───────┴─────────┘

As a composable database engine, I think it make sense to provide a config to customize the default behavior of null ordering.

What changes are included in this PR?

This PR introduces a new parser option default_null_ordering:

        /// Specifies the default null ordering for query results. There are 4 options:
        /// - `nulls_max`: Nulls appear last in ascending order.
        /// - `nulls_min`: Nulls appear first in ascending order.
        /// - `nulls_first`: Nulls always be first in any order.
        /// - `nulls_last`: Nulls always be last in any order.
        ///
        /// By default, `nulls_max` is used to follow Postgres's behavior.
        /// postgres rule: <https://www.postgresql.org/docs/current/queries-order.html>
        pub default_null_ordering: String, default = "nulls_max".to_string()

There are 4 cases for the null ordering. nulls_max is used by default to follow the Postgres's behavior.

Are these changes tested?

• add sqllogictests.
• It's picked from the Wren AI fork Allow to set up the default null ordering Canner/datafusion#3 and it's used in the production for a while.

Are there any user-facing changes?

add a new config.

[alamb]

Thank you @goldmedal -- this looks great to me. I had some small suggestions but nothing I think is required

[goldmedal]

Thanks @alamb for reviewing 👍