Unlike ComputerThread, we do not have a single source of tasks, and so
need a smarter way to handle scheduling and rate limiting. This
introduces a cooldown system, which works on both a global and
per-computer level:
Each computer is allowed to do some work for 5ms. If they go over that
budget, then they are marked as "hot", and will not execute work on the
next tick, until they have cooled down. This ensures that _on average_
computers perform at most 5ms of work per tick.
Obviously this is a rather large time span, so we also apply a global
10ms to all computers. This uses the same cooldown principle, meaning we
keep to an average of 10ms, even if we go over budget.
This allows us to track how much work various peripherals are doing.
This will not work with all systems, such as Plethora, as that has its
own execution system.
