MySQL doesn't support the NULLS FIRST/LAST clause in ORDER BY statements

[phillipleblanc]

Describe the bug

When unparsing LogicalPlans back to SQL statements for the MySQL dialect, any plan that includes a Sort node will produce a SQL statement that looks like:

SELECT "ta"."j1_id" FROM "j1" AS "ta" ORDER BY "ta"."j1_id" ASC NULLS LAST LIMIT 10
                                                                ^--------^              

The NULLS LAST causes issues when run against a MySQL server, as it doesn't recognize that syntax.

To Reproduce

Create an Unparser with a MySQL dialect, unparse any plan that includes a Sort node and observe that the SQL string generated includes the NULLS FIRST/LAST clause.

Expected behavior

The MySQL dialect should omit writing out the NULLS LAST clause, since its not a supported feature of the DB.

Additional context

No response