Currently, the default for scrape_protocols in the scrape config is set dynamically depending on the (locally effective) setting of scrape_native_histograms. This is mostly done so that non-users of native histograms aren't suddenly using protobuf to scrape.

However, this dynamic default is very confusing (to implement and to document). In v4, we should return to a "static" default value for scrape_protocols. From the current perspective, that would be a "protobuf first" value, namely [ PrometheusProto, OpenMetricsText1.0.0, OpenMetricsText0.0.1, PrometheusText1.0.0, PrometheusText0.0.4 ]. However, by the time v4 drops, we might want to prefer a different list. In any case, the default should just always be the same.