Re: bin/60383: fssconfig(8): distinguish between taking and loading a snapshot

Would also be nice if creating and mounting a snapshot didn't require
specifying an fssN device, just like dumping a snapshot with dump(8)
doesn't require that.

For example, perhaps the interface could look something like:

- Take a snapshot without mounting it:

	# snapfs /home /home/.snap/20260718

- Mount a snapshot:

	# mount -t snapshot /home/.snap/20260718 /mnt

Under the hood, it might be nice if /dev/fss were a cloning device so
programs could just open("/dev/fss") without having to allocate an
fssN unit themselves.