[jOOQ/jOOQ#7421] Render "dual" as a name

The `DUAL` table will now be rendered as a `Name` rather than as the
plain string `dual`. This way it will also adhere to the name case
settings in the rendered SQL.

jOOQ/src/main/java/org/jooq/impl/Dual.java

@@ -191,7 +191,7 @@ final class Dual extends AbstractTable<Record> {
 
 
                 default:
-                    ctx.sql("dual");
+                    ctx.visit(N_DUAL);
                     break;
             }
         }