gnome-initial-setup-copy-worker and gnome-keyring (and others) used to be
started automatically by the session manager during the
GSM_MANAGER_PHASE_INITIALIZATION phase. This is racy because gnome-keyring
could read its file ~/.local/share/keyrings/login.keyring before it is written
by gnome-initial-setup-copy-worker. The correct solution is to wait
gnome-initial-setup-copy-worker finishes before starting other components in
the initialization phase.

I want to enforce this order without adding knowledge of gnome-initial-setup in
gnome-keyring and others. It must also work on systems which don't use
gnome-initial-setup. So I don't use a flag file in gnome-keyring's
AutostartCondition to delay its startup.

Instead, I add a new phase GSM_MANAGER_PHASE_EARLY_INITIALIZATION before the
initialization phase. If no autostart desktop files use that phase,
gnome-session will just go on to the next phase. But if
gnome-initial-setup-copy-worker uses this new pha...