otel metrics: define histogram buckets the same as before

[syphar]

I was super confused why percentiles looked so different in datadog.

This is the reason.

The problem was that the default histgram buckets are so different between

• prometheus and
• opentelemetry

Also I now learned something about histograms & buckets :)

Now I

• set the same buckets as before, where we did have buckets overridden before
• also set response time buckets now, to the default from the opentelemetry semantic conventions.
• ( also set the new response time buckets on the prometheus metric to be able to compare)