Measure client up/down bandwidth for directory requests, split by type
See parent ticket for context.
We need a way to measure, over time, split up by type of directory request, how much bandwidth a client uses for requests and for responses.
We should include both directory lookups that are successful and those that are not.
We should, if possible, measure this with and without circuit overhead. But not if it's too hard.
We should, if possible, count failed circuits that are opened only for directory requests. But not if it's too hard.