Return some indication that there are named connections with SHOW SLAVE STATUS with Multi Source Replica

When multi source replica even with just one named connection SHOW SLAVE STATUS returns empty results:

MariaDB [(none)]> show slave status\G

Empty set (0.000 sec)

MariaDB [(none)]> show all slaves status\G

*************************** 1. row ***************************

               Connection_name: ext_repl

               Slave_SQL_State: Waiting for room in worker thread event queue

                Slave_IO_State: Waiting for master to send event

I think it would be useful to have an indication that the server is actually replicating on some other "channel".
Maybe also just convert SHOW SLAVE STATUS to behave as SHOW ALL SLAVES STATUS by default, in such case it will always do the right thing showing all the channels if present or the default one in all other cases.