Epochs returned by `eidaws-stationlite` for `service=station&level=network|station`

[damb]

At the time being all epochs returned by eidaws-stationlite are based on the underlying ChannelEpochs.

In the context of stream epoch canonicalization this is not ideal when querying fdsnws-station metadata for level=network|station. Instead, it would be better to rely on the underlying NetworkEpoch or rather StationEpoch, respectively, in order to maximize cache hit performance.