Users can't run an anonymous client and non-anonymous single
onion service at the same time. We need to know whether we have
any client ports or sockets open to do this check.

When determining whether a client port (SOCKS, Trans, NATD, DNS)
is set, count unix sockets when counting client listeners. This
has no user-visible behaviour change, because these options are
set once and never read in the current tor codebase.

Don't count sockets when setting ControlPort_set, that's what
ControlSocket is for. (This will be reviewed in #19665.)

Don't count sockets when counting server listeners, because the code
that uses these options expects to count externally-visible ports.
(And it would change the behaviour of Tor.)