Implement/test new server ORDER BY implementation

MDEV-14500 implements ORDER BY in a way that removes our need for postion()/rnd_pos(). If there are any implementation tasks for this it should be tracked here.

Description: Hi,
during the execution of a simple query an a simple 2000 rows Columnstore table, we have this exception:

Error Code: 1815
Internal error: IDB-2015: Sorting length exceeded. Session variable max_length_for_sort_data needs to be set higher

To reproduce (quote from customer ticket)

Create Table: CREATE TABLE `campagna_web_codice` (
`cwc_id` int(11) DEFAULT NULL,
`cwc_cw_id` int(11) DEFAULT NULL,
`cwc_cd_id` int(11) DEFAULT NULL,
`cwc_codice` varchar(30) DEFAULT NULL,
`cwc_va_id` int(11) DEFAULT NULL,
`cwc_prezzo` decimal(12,2) DEFAULT NULL,
`cwc_prezzoListino` decimal(12,2) DEFAULT NULL,
`cwc_prezzoSpedizione` decimal(8,2) DEFAULT NULL,
`cwc_in_id` int(11) DEFAULT NULL,
`cwc_na_id` int(11) DEFAULT NULL,
`cwc_desc` varchar(100) DEFAULT NULL,
`cwc_datainizio` date DEFAULT NULL,
`cwc_datafine` date DEFAULT NULL,
`cwc_mo_id` int(11) DEFAULT NULL,
`cwc_ma_id` int(11) DEFAULT NULL,
`cwc_pd_id` int(11) DEFAULT NULL,
`cwc_set_id` int(11) DEFAULT NULL,
`cwc_mr_id` int(11) DEFAULT NULL,
`cwc_ca_id` int(11) DEFAULT NULL,
`cwc_fa_id` int(11) DEFAULT NULL,
`cwc_ti_id` int(11) DEFAULT NULL,
`cwc_azws` longtext DEFAULT NULL
) ENGINE=Columnstore DEFAULT CHARSET=utf8

The query is as simple as :

select * from dmc_dg_ita_1.campagna_web_codice order by 1 DESC limit 0, 1000;

we tried to raise max_length_for_sort_data up to 51200 (1024 is the default value), but with no success.

If we delete "cwc_azws" row (longtext), we get the result correctly.