Rename kiod5 to kiod6

To give the postfix more meaning again. That postfix perhaps also could be dropped, due to being in the KF6-prefixed libexec path? Though the postfix helps finding the variant in system process lists, next to any KF5 one?

Talking about next to KF5 one:

I wonder though how the D-Bus services provided by the respective plugins should coexist with the KF5 variants? Currently they register for the same unversioned well-known D-Bus service name, if I saw correctly, also by the service description file they install. Does anyone remember how this was solved for kdelibs4 (where all the plugins though were still in kded) in parallel to KF5? The kpasswdserver plugin from kde4's runtime also used the well-known D-Bus service name "org.kde.kpasswdserver".