Support realtime execution with guarantees

[cassava]

When hooking Cloe up to a HiL system, we need to make sure that the controller attached to the HiL system is "triggered" at regular intervals: not too early and not too late.

Problems:

• Cloe is not designed for this use-case, we perform too many heap allocations and use algorithms that cannot guarantee that they will return within some deadline.
• Cloe is not developed or tested on realtime systems.

A naiive approach would be to simply add a trigger event that fires when we miss the realtime_factor. This isn't quite so simple.