Remove publishing average

[jonatan-ivanov]

Remove publishing avg for those registries where this is applicable: they currently publish avg and it can be removed (the protocol lets us), e.g.: Datadog.

Averages are usually not very useful in terms of latency and can be the source of confusion, they are also not aggregatable. Removing them would also save cost but this is a breaking change.

[shakuzen]

We could also consider a step before this which would be to flip the default from publishing average to not publishing it, but that would also be a breaking change, albeit with a fallback to the prior behavior.