Remove journald-console generator

snapd_recovery_mode kernel parameter is not enough to know whether we
need to forward messages to the console. To be able to know we need
the modeenv. Journald has to be started way before that. Journald
configuration cannot be reloaded. And we should not restart journald.

Users can still add `systemd.journald.forward_to_console=1` the kernel
command line if they need to debug the install.