infra: prototype running Linux in a jailed bhyve

[skhal]

Goal: enjail bhyve running any Linux distribution.

Lab runs Ubuntu 24.04 in a jail using FreeBSD Linux binary compatibility layer:

1. It does not really run a Linux kernel. The FreeBSD kernel emulates Linux kernel API for Ubuntu environment to work.
2. The jail still runs FreeBSD environment with rc-scripts. These in turn start Linux services under chroot(1). Such setup adds yet another layer between Linux environment and FreeBSD hosting node.
3. Some of the packages installed with apt (or other applications) require deep integration with systemd(1) in pre-/post-install scripts and fail without Linux kernel.

This prototype evaluates feasibility of running full Linux under FreeBSD.