Statsd receiver incorrect handling of histogram/timer sample rate

[jmacd]

Describe the bug

The statsdreceiver has a syntax for sampled histogram and timer events. The line has metric type "h" or "ms" and an "@Rate" member to indicate sampling. When this occurs, the consumer is meant to observe 1/rate (i.e., the adjusted count) number of identical events with a certain value.

Today's code is treating the histogram/timer value like a counter, i.e., scaling the value by the adjusted count.

Steps to reproduce

Happens here:

opentelemetry-collector-contrib/receiver/statsdreceiver/protocol/statsd_parser.go

Line 315 in df528f6

f = f / result.sampleRate

What did you expect to see?
The code needs a bit of restructuring before this can be easily fixed. The montanaflynn/stats package does not have the method we would need to easily implement this.

What did you see instead?

Instead of montanaflynn/stats, I think we should use the Prometheus golang client's summary data structure directly.

Additional context
The term "adjusted count" is defined in OTEP 170 as the inverse of sampling probability