This change moves the OpenDC modules previously living in the simulator/opendc
directory to the simulator directory itself given that we do not make a
distinction between OpenDC and odcsim anymore.

This change eliminates the use of Domain and simulationContext in favour
of the generic (Test)CoroutineScope and Clock classes. In this way, we
decouple the OpenDC modules and their logic from simulation-related
code.

In this way, we also simplify eventual attempt for emulating OpenDC
componments in real-time.

This change prepares the simulator Git repository for the monorepo residing at
https://github.com/atlarge-research.com/opendc. To accomodate for this, we
move all files into a simulator subdirectory.