feat: report listening sockets

get_listening_sockets() in the shape of napalm-device-types'
ListeningSocketsMixin, whose ss/cgroup reading is Linux's, and with its
rule: read as root first, and without root when that brings nothing back,
which the reading reports as `attributed: False`.

- FreeBSD: `sockstat -46lq -P tcp,udp`, which sees every socket either way.
- OpenBSD: `fstat -n` as root (the sockets nothing is connected to; port 0
  is unbound), `netstat -an` without root, as fstat shows a user only
  their own processes; those sockets come without a process.
- Addresses as ss prints them: `*` becomes 0.0.0.0 or :: by family, IPv6
  without brackets, a zone (`fe80::1%lo0`) becomes the interface. One entry
  per socket, the first process holding it.

No get_kernel_facts on purpose: KernelFactsMixin reports a Linux kernel's
modules and CONFIG_ options, which a BSD kernel does not have.

Fixtures recorded on the FreeBSD 15.1 and OpenBSD 7.9 VMs with test
listeners on 127.0.0.1 and ::1 (NetOrk/netork#798).

tests/test_drivers.py

@@ -193,3 +193,34 @@ class TestAccountsAndProcesses:
             "schedule": "0 4 * * *",
             "command": "/home/netork/backup.sh",
         } in jobs
+
+
+class TestListeningSockets:
+    def test_freebsd_as_root_is_attributed(self):
+        driver = _driver(FreeBSDDriver, {})
+        sockstat = _read("freebsd-vm", "sudo_sockstat_46lq_P_tcp_udp.txt")
+        driver.run_command = lambda command, privileged=False, timeout=60, stdin=None: (  # type: ignore[method-assign]
+            type("R", (), {"stdout": sockstat, "exit_code": 0})()
+        )
+        result = driver.get_listening_sockets()
+        assert result["attributed"] is True
+        assert len(result["sockets"]) == 7
+
+    def test_openbsd_without_root_falls_back_to_netstat(self):
+        driver = _driver(OpenBSDDriver, {})
+        netstat = _read("openbsd-vm", "netstat_an.txt")
+        calls = []
+
+        def run(command, privileged=False, timeout=60, stdin=None):
+            calls.append((command, privileged))
+            if privileged:  # sudo -n without a password: refused
+                return type("R", (), {"stdout": "", "exit_code": 1})()
+            return type("R", (), {"stdout": netstat, "exit_code": 0})()
+
+        driver.run_command = run  # type: ignore[method-assign]
+        result = driver.get_listening_sockets()
+        assert result["attributed"] is False
+        assert ("tcp", "0.0.0.0", 22) in {
+            (s["proto"], s["address"], s["port"]) for s in result["sockets"]
+        }
+        assert calls == [("fstat -n", True), (OpenBSDDriver.LISTENING_FALLBACK_COMMAND, False)]