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 introduces the SimProcessingUnit which represents a
simulated processing unit which the user can control during the workload
execution.

This change adds an experiment for the OpenDC Energy project, which
tests various energy models that have been implemented in OpenDC.

This change updates the SimHost implementation to use BatchRecorder to
batch record multiple metrics at once.

This change removes the StateFlow speed property on the
SimResourceSource, as the overhead of emitting changes to the StateFlow
is too high in a single-thread context. Our new approach is to use
direct callbacks and counters.

This change adds a model implementing Dynamic Voltage Frequency Scaling
(DVFS) to OpenDC.

This change updates the compute service simulator to use OpenTelemetry
for reporting metrics of the (simulated) hosts as opposed to using
custom event flows.

This approach is more generic, flexible and possibly offers better
performance as we can collect metrics of all services in a single sweep,
as opposed to listening to several services and each invoking the
handlers.

This change integrates the OpenTelemetry Metrics API in the OpenDC
Compute Service implementation. This replaces the old infrastructure for
gathering metrics.

This change changes the compute service and users of the compute service
to not rely on the internals of `ComputeServiceImpl` and instead use its
public API.

This change moves the power models from the `opendc-compute-simulator`
to the `opendc-simulator-compute` module, since it better fits the scope
of the models and allows them to be re-used for other purposes.