Epic: Refactor VM internals

[Omrigan]

This is a broad epic aimed to collect a number of related issues, and to coordinate the efforts to solve them.

Motivation

We have a number of problems with the current architecture, some examples are:

1. dmesg logs can interleave with normal programs #1115
2. Add a clear indication of why resize-swap fails #958
3. Properly handle initialization failures inside the VM #1094

Plus those listed in #728 and #835

DoD

1. We should have a single dockerfile for neonvm runtime, and vm-builder should do very little beyond converting docker image to qcow2
2. Architecture doesn't prevent us from running custom non-compute payload
3. Subtask bugs are fixed

Implementation ideas

TLDR: switch to systemd and turn compute image into a container.