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/openbsd-vm/syspatch_c.txt

@@ -0,0 +1,34 @@
+001_xserver
+002_smtpd
+003_vmd
+004_elf
+005_sysv
+006_nfs
+007_ipsec
+008_npppd
+009_iked
+010_ifioctl
+011_nipledge
+012_kernproc
+013_ttyioctl
+014_expat
+015_smtpd
+016_nfs
+017_wscons
+018_shmat
+019_expat
+020_xserver
+021_ldapd
+022_nsd
+023_unbound
+024_libressl
+025_procargs
+026_sysvipc
+027_iked
+028_wgbind
+029_sysvsem
+030_uidrange
+031_isakmpd
+032_xserver
+033_expat
+034_wsdisplay