drop kwallet support in favor of org.freedesktop.secrets

While I was investigating the reimplementation of the kwallet module with sd-bus in place of libdbus, I found out that kwallet recently merged support for org.freedesktop.secrets https://invent.kde.org/frameworks/kwallet/-/merge_requests/11.

Which is a generic D-Bus interface for storing secrets that is also used by gnome-keyring.

We already support this interface through the libsecret module. Meaning after release and adoption of distribution the kwallet module will be made obsolete.

reference: https://wiki.gnome.org/Projects/Libsecret (ksecretservice seams to have been abandoned) https://specifications.freedesktop.org/secret-service/latest/