This also stops using -1 as auth failed, and moves all failure statuses
to positive numbers. It looks like Exiting with -1 ends up setting the
status to 255 on exit, but then in the locker, it sees this as 255 and
not -1, since things get coerced into 32-bit integers.
If the user presses enter or escape in order to get the unlock dialog to
show in the first place, forwarding that event to the dialog will only
cause it to close immediately.
Also took the opportunity to clean up the dependencies where I have my
own patches. I'm now using the cargo 'patch' section so that the
dependencies specified in the individual Cargo.toml files are clean.
By default it'll look at your environment to try to figure out which
display manager is used in order to start a new session. We first try
the org.freedesktop.DisplayManager dbus interface, and if that fails,
inspect XDG_SESSION_DESKTOP to try to figure out which display manager
is running.
The user can also still specify the correct display manager, or a custom
command.
This includes an abortive attempt to do a gtk4 dialog (which I don't
think is possible, as gtk4 doesn't allow embedding toplevels anymore),
and an iced dialog, which I just never started writing.
