We don't actually need to define separate user_data argument for
each method handler and property getter/setter. Instead, we can define
one argument for the whole object. That will make it easier to register
objects like BSS or Networks which require allocating and freeing
memory for their arguments.
This was mostly identical code that had been copied for the new D-Bus
API implementation and as such, should really have been shared from
the beginning. In addition, the copied code ended up generating
interesting stack traces since the actual D-Bus connection was being
shared even though the pointer to it was stored in two distinct
data structures. The old D-Bus code ended up dispatching some
D-Bus callbacks which ended up running the new D-Bus code.
Since the private context pointers were mostly identical, everything
seemed to more or less work, but this design was just making things
more complex and potentially very easy to break.
The D-Bus interface does not really have anything to do with the
wpa_supplicant ctrl_iface interface and as such, this prefix in
dbus files is both confusing and unnecessarily. Make the file names
shorter by removing this prefix.
