Preserve ORDER BY in Unparser for projection -> order by pattern (#19483)

Because of #15886 a parse -> unparse -> parse loop changed the query so
that it would give incorrect results.

Author: adriangb

datafusion/core/tests/sql/mod.rs

@@ -70,6 +70,7 @@ mod path_partition;
 mod runtime_config;
 pub mod select;
 mod sql_api;
+mod unparser;
 
 async fn register_aggregate_csv_by_sql(ctx: &SessionContext) {
     let testdata = test_util::arrow_test_data();