dmesg logs can interleave with normal programs

[sharnoff]

Problem description

Inside our VMs, all output is aggregated into a single stream. Sometimes this causes logs from the kernel to cut off other logs mid-line, making them much harder to search.

There's also a handful of examples linked in the comments on #578.

This isn't a frequent problem by any means, but it prevents being able to rely on the quality of the logs from our VMs (hence: why this issue is marked as tech debt).

Implementation ideas

A simpler idea could be to direct dmesg output to /dev/console and everything else to some virtio serial device, so that any interleaving would be purely between normal user programs.

Or, implementing #578 might also fix this issue.