feat: FreeBSD and OpenBSD drivers, read side

FreeBSDDriver (`freebsd`) and OpenBSDDriver (`openbsd`) on a shared
BsdDriver, for the BSD VMs netOrk provisions and BSD hosts added by hand
(NetOrk/netork#798).

- SSH over exec channels (napalm-device-types' run_on_transport): no PTY,
  stdout and stderr apart, real exit codes; run_command()/open_stream()
  are public. Root through `sudo -S` with the password on stdin, or
  `sudo -n` without one.
- Facts: hostname, release and running kernel (freebsd-version / uname),
  hardware from SMBIOS (kenv) or hw.* sysctls, uptime from kern.boottime.
- Interfaces and addresses (ifconfig -a: ether/lladdr, hex netmasks,
  scoped IPv6), routes (netstat -rn, OpenBSD's abbreviated networks
  written out, host/broadcast/loopback entries left out), ARP (FreeBSD's
  sentences, OpenBSD's table), users and groups, processes (lstart read as
  one five-word field), cron jobs (system crontab and the login user's).
- Parsers are pure functions, tested on output recorded from FreeBSD 15.1
  (hand-installed and cloud image) and OpenBSD 7.9 (NetOrk/netork#793),
  with internal addresses replaced by documentation ranges.

napalm_bsd/openbsd.py

@@ -0,0 +1,30 @@
+"""OpenBSD: hw.* sysctls for the hardware, uname for release and kernel."""
+
+from __future__ import annotations
+
+from napalm_device_types import FingerprintRule
+
+from napalm_bsd.base import BsdDriver
+
+
+class OpenBSDDriver(BsdDriver):
+    """NAPALM driver for OpenBSD hosts, over SSH."""
+
+    TYPE_LABEL = "OpenBSD"
+    VENDOR = "OpenBSD"
+    DRIVER_NAME = "openbsd"
+    # OpenBSD's SSH banner names no OS; its sysDescr does ("OpenBSD host 7.9 GENERIC.MP#449").
+    SNMP_FINGERPRINT = [FingerprintRule("openbsd", weight=5.0)]
+
+    OS_VERSION_COMMAND = "uname -sr"
+    # The kernel's build, e.g. GENERIC.MP#449; the release is in uname -r.
+    KERNEL_COMMAND = "uname -v"
+    # A sysctl node the machine lacks fails on its own and prints nothing.
+    PLATFORM_COMMAND = (
+        "for k in vendor product serialno; do "
+        'printf "%s=%s\\n" "$k" "$(sysctl -n hw.$k 2>/dev/null)"; done'
+    )
+
+    def _hardware(self) -> tuple[str, str, str]:
+        hw = self._platform()
+        return hw.get("vendor", ""), hw.get("product", ""), hw.get("serialno", "")