graphics: Introduce a separate daemon for the boot log

The daemon responsible for the boot log must never ever block to avoid deadlocks, but doing so while still accepting keyboard input is non-trivial. This commit splits the boot log out from fbcond into a separate daemon to make this a lot easier to implement. This also allows making fbcond blocking again, which simplifies it a fair bit.

Needs to be merged together with cookbook!431 (merged)