Change all DBUS_TYPE_G_UCHAR_ARRAY properties to G_TYPE_BYTES, and
update corresponding APIs. Notably, this means they are now refcounted
rather than being copied.

Update the rest of NM for the changes. The daemon still converts SSIDs
to GByteArrays internally, because changing it to use GBytes has lots
of trickle-down effects. It can possibly be changed later.