Add new port sysutils/bvm

The BVM is a Bhyve virtual machine management tool
based on FreeBSD that allows you to easily manage virtual machines.

1. The supported operating systems are: FreeBSD,OpenBSD,NetBSD,Debian,OpenSuse,Ubuntu Windows10 etc.
2. Supports multiple network cards and multiple hard disks.
3. There are two kinds of network modes: Bridged and NAT
4. Support grub and uefi boot
5. Support for ZFS

PR: 229407
Submitted by: guoqiang_cn@126.com (maintainer)
Reviewed by: ygy, yuri
Differential Revision: https://reviews.freebsd.org/D16074