backends/kwayland: use the connector name
requested to merge work/zamundaaa/cherry-pick-5305b81ef3c366f8bc99cfb05e8a4273f1b29f60 into Plasma/5.26
Output::name is used in configs as the connector name, if the Wayland backends sets something else, logic for de-duplication of outputs with the same EDID doesn't work anymore
(cherry picked from commit 5305b81e)