PAM configuration changes needed for new KScreenLocker feature in Plasma 6

[David Edmundson]

We can definitely ship the files. We used to.

I'm surprised we need to ship the stock "kde" file, in theory it
should roll back to a stock file. As per the docs:

>       The service_name argument specifies the name of the service to
       apply and will be stored as PAM_SERVICE item in the new context.
       The policy for the service will be read from the file
       /etc/pam.d/service_name or, if that file does not exist, from
       /etc/pam.conf.

Maybe that's not set up everywhere.
Distro customisation may still be needed because some certain
distribution do weird things.

We don't need to involve SDDM, they're completely separate as far as
this is concerned.

>> This reminds me, what happened to the idea of us shipping an SDDM fork?

Not blocked, not being rushed for 6.0
https://invent.kde.org/plasma/plasma-desktop/-/issues/91#note_729760

> Do we need an SDDM release for the MegaReleases?

Without an SDDM release you won't get the plasma theme. So for
February, it's a target
We don't need it for the alpha, and even using git master wouldn't
achieve anything in this regard.

David