Pipeline steps don't currently support modeling their status. We should add this so we can track if steps are waiting, running, or completed. The status should also capture completion state.

• Introduce a new PipelineStepStatus enum.

enum PipelineStepStatus {
    Pending,
    Running,
    Succeeded,
    Failed,
    Canceled
}

• Add a Status property to a PipelineStep
• Update the DistributedApplicationPipeline to set the status on each of those steps