Add logic to generateFreeBSDUserData to allow for an SSH connection as root for FreeBSD. Add FreeBSD test cases to ssh_test that exercise the same paths as the existing Ubuntu tests but for BSD. Updates https://github.com/tailscale/corp/issues/44813 Updates https://github.com/tailscale/tailscale/issues/13038 Signed-off-by: Mario Minardi <mario@tailscale.com>