This change updates the project structure to become flattened.
Previously, the simulator, frontend and API each lived into their own
directory.

With this change, all modules of the project live in the top-level
directory of the repository. This should improve discoverability of
modules of the project.

This change removes the opendc-core module. This module was an artifact
of the old codebase and remained mostly unused. This change removes all
usages of the module and if necessary introduces replacement classes.

This change removes the SimWorkloadImage implementation and changes
Image to a data class without workload. Simulation workloads should now
be pased via image metadata as the image storage should be unaware of
any simulation details.

This change converts the low-level workload model to be pull-based. This
reduces the overhead that we experienced with our previous co-routine
based approach.

This change splits the opendc-compute module into two modules:

  1. opendc-compute-core
     The interfaces and APIs that represent a IaaS platform.
  2. opendc-compute-simulator
     The implementation of these interfaces using simulation components
     from opendc-simulator-compute.

This change updates the remainder of the codebase to use the
opendc-simulator-compute module for the simulation of workloads.

This change moves the OpenDC simulator codebase to the org.opendc
namespace of which we control the domain. Previously, we used the
com.atlarge package of which we did not control the domain, which might
lead to difficulties in the future.

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.