remove `Aggregate.dict()`, `TimeValue.dict()`.

[bmario]

This method is used in parsing HistoryResponse in the metricq-grafana endpoint for the timeline request.
The active_time attribute would allow us to draw the last (or only) aggregate in the MetricQ-Webview.

[tilsche]

I'm not sure I even like the dict there at all. I mean sure we can add active_time. But in general it seems arbitrary whether to use mean, and/or sum, integral etc... Isn't that more consumer dependent? What's the advantage to have that decision encoded in the interface?

[bmario]

Actually, we don't touch the dict in metricq-grafana, but pass that down as is to metricq-js. That was the whole point of the timeline endpoint/query there

[tilsche]

We discussed to deprecate / delete the dict function and do the conversion in metricq-grafana