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/freebsd.py

@@ -0,0 +1,38 @@
+"""FreeBSD: kenv for the hardware, freebsd-version for base and kernel."""
+
+from __future__ import annotations
+
+from napalm_device_types import FingerprintRule
+
+from napalm_bsd.base import BsdDriver
+
+
+class FreeBSDDriver(BsdDriver):
+    """NAPALM driver for FreeBSD hosts, over SSH."""
+
+    TYPE_LABEL = "FreeBSD"
+    VENDOR = "FreeBSD"
+    DRIVER_NAME = "freebsd"
+    SNMP_FINGERPRINT = [FingerprintRule("freebsd", weight=5.0)]
+    # OpenSSH in FreeBSD's base names it in its banner ("OpenSSH_9.9 FreeBSD-20250219").
+    SSH_FINGERPRINT = [FingerprintRule("freebsd", weight=3.0)]
+
+    HOSTNAME_COMMAND = "sysctl -n kern.hostname"
+    # Userland and running kernel; both carry the patch level (15.1-RELEASE-p4).
+    OS_VERSION_COMMAND = "freebsd-version -u"
+    KERNEL_COMMAND = "freebsd-version -r"
+    # kenv takes one variable per call, and a missing one fails the call.
+    PLATFORM_COMMAND = (
+        "for k in maker product serial; do "
+        'printf "%s=%s\\n" "$k" "$(kenv -q smbios.system.$k)"; done'
+    )
+    # -W: FreeBSD cuts long destinations to the column width otherwise.
+    ROUTES_COMMAND = "netstat -rnW"
+
+    def _os_version(self) -> str:
+        version = super()._os_version()
+        return f"FreeBSD {version}" if version else ""
+
+    def _hardware(self) -> tuple[str, str, str]:
+        smbios = self._platform()
+        return smbios.get("maker", ""), smbios.get("product", ""), smbios.get("serial", "")