consider extending `IActivity` with `IActivityWithThroughput<IDisposable>`

[BryanWilhite]

the IActivity space in the Core recognizes input and output but not throughput (which I argue is characteristic of types implementing IDisposable); the following intends to address throughput:

public interface IActivityWithThroughput<IDisposable> : IActivity
{
    void Start(Action<IDisposable> throughputAction)
}

public interface IActivityWithTaskThroughput<IDisposable> : IActivity
{
    Task StartAsync(Action<IDisposable> throughputAction)
}

📖 http://songhayblog.azurewebsites.net/entry/2021-06-26-studio-status-report-2021-06/