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.

tests/fixtures/freebsd-host/cat_etc_group.txt

@@ -0,0 +1,39 @@
+wheel:*:0:root
+daemon:*:1:
+kmem:*:2:
+sys:*:3:
+tty:*:4:
+operator:*:5:root
+mail:*:6:
+bin:*:7:
+news:*:8:
+man:*:9:
+games:*:13:
+ftp:*:14:
+staff:*:20:
+sshd:*:22:
+smmsp:*:25:
+mailnull:*:26:
+guest:*:31:
+video:*:44:
+realtime:*:47:
+idletime:*:48:
+bind:*:53:
+unbound:*:59:
+proxy:*:62:
+authpf:*:63:
+_pflogd:*:64:
+_dhcp:*:65:
+uucp:*:66:
+dialer:*:68:
+network:*:69:
+audit:*:77:
+www:*:80:
+u2f:*:116:
+ntpd:*:123:
+_ypldap:*:160:
+hast:*:845:
+tests:*:977:
+nogroup:*:65533:
+nobody:*:65534:
+netork:*:1001: