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_passwd.txt

@@ -0,0 +1,28 @@
+root:*:0:0:Charlie &:/root:/bin/sh
+toor:*:0:0:Bourne-again Superuser:/root:
+daemon:*:1:1:Owner of many system processes:/root:/usr/sbin/nologin
+operator:*:2:5:System &:/:/usr/sbin/nologin
+bin:*:3:7:Binaries Commands and Source:/:/usr/sbin/nologin
+tty:*:4:65533:Tty Sandbox:/:/usr/sbin/nologin
+kmem:*:5:65533:KMem Sandbox:/:/usr/sbin/nologin
+games:*:7:13:Games pseudo-user:/:/usr/sbin/nologin
+news:*:8:8:News Subsystem:/:/usr/sbin/nologin
+man:*:9:9:Mister Man Pages:/usr/share/man:/usr/sbin/nologin
+sshd:*:22:22:Secure Shell Daemon:/var/empty:/usr/sbin/nologin
+smmsp:*:25:25:Sendmail Submission User:/var/spool/clientmqueue:/usr/sbin/nologin
+mailnull:*:26:26:Sendmail Default User:/var/spool/mqueue:/usr/sbin/nologin
+bind:*:53:53:Bind Sandbox:/:/usr/sbin/nologin
+unbound:*:59:59:Unbound DNS Resolver:/var/unbound:/usr/sbin/nologin
+proxy:*:62:62:Packet Filter pseudo-user:/nonexistent:/usr/sbin/nologin
+_pflogd:*:64:64:pflogd privsep user:/var/empty:/usr/sbin/nologin
+_dhcp:*:65:65:dhcp programs:/var/empty:/usr/sbin/nologin
+uucp:*:66:66:UUCP pseudo-user:/var/spool/uucppublic:/usr/local/libexec/uucp/uucico
+pop:*:68:6:Post Office Owner:/nonexistent:/usr/sbin/nologin
+auditdistd:*:78:77:Auditdistd unprivileged user:/var/empty:/usr/sbin/nologin
+www:*:80:80:World Wide Web Owner:/nonexistent:/usr/sbin/nologin
+ntpd:*:123:123:NTP Daemon:/var/db/ntp:/usr/sbin/nologin
+_ypldap:*:160:160:YP LDAP unprivileged user:/var/empty:/usr/sbin/nologin
+hast:*:845:845:HAST unprivileged user:/var/empty:/usr/sbin/nologin
+tests:*:977:977:Unprivileged user for tests:/nonexistent:/usr/sbin/nologin
+nobody:*:65534:65534:Unprivileged user:/nonexistent:/usr/sbin/nologin
+netork:*:1001:1001:netOrk:/home/netork:/bin/sh