This patch removes startup of window manager out of KSMServer. It also removes the usage of SM protocol to talk to KWin.
This was problematic for two reasons. We weren't completely spec compliant making custom changes to handle the window manager specially. It also requires ksmserver up first as with QSessionManager we can only pass the restoration ID along as a command line argument.
We need to have the detachment so that we get session restore on kwin wayland for X clients, as well supporting the systemd boot which can't load from ksmserver's session config.
Instead, KWin is told to save and restore on DBus directly.