Modify command, query and event dispatchers to allow generic types

[lukwat]

Please use something similar to following instructions:

            var eventType = @event.GetType();
            var handlerType = typeof(IEventHandler<>).MakeGenericType(eventType);

            using var scope = _serviceFactory.CreateScope();
            dynamic handlers = scope.ServiceProvider.GetServices(handlerType);

            foreach (var handler in handlers)
            {
                if (handler == null)
                    return;

                await handler.HandleAsync((dynamic) @event);
            }