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 migrates the remainder of the codebase to the
SimulationCoroutineDispatcher implementation.

This change introduces the SimulationCoroutineDispatcher implementation
which replaces the TestCoroutineDispatcher for running single-threaded
simulations.

Previously, we used the TestCoroutineDispatcher from the
kotlinx-coroutines-test modules for running simulations. However, this
module is aimed at coroutine tests and not at simulations.

In particular, having to construct a Clock object each time for the
TestCoroutineDispatcher caused a lot of unnecessary lines. With the new
approach, the SimulationCoroutineDispatcher automatically exposes a
usable Clock object.

In addition to ergonomic benefits, the SimulationCoroutineDispatcher is
much faster than the TestCoroutineDispatcher due to the assumption that
simulations run in only a single thread. As a result, the dispatcher
does not need to perform synchronization and can use the fast
PriorityQueue implementation.

This change migrates the OpenDC codebase to use the new FilterScheduler
for scheduling virtual machines. This removes the old allocation
policies as well.

This change adds an implementation of the filter scheduler to the OpenDC
Compute module. This is modeled after the filter scheduler
implementation in OpenStack and should allow for more flexible
scheduling policies.

See: https://docs.openstack.org/nova/latest/user/filter-scheduler.html

This change fixes an issue in the RandomAllocationPolicy where it would
incorrectly obtain the required memory for the server.

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 removes the event tracer from the OpenDC Workflow service as
we start migrating to the industry standard OpenTelemetry.

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

This change removes the dependency on the event tracer in
`opendc-trace`, since we are in the process of migrating OpenDC to
use OpenTelemetry for distributed tracing and metrics.