Add chproxy as the prometheus metrics namespace or prefix

[bzon]

It would be nice if the metrics will have a namespace chproxy which will prefix each metrics with chproxy_.

E.g. chproxy_request_success_total instead of just request_success_total

The problem is that the metric names are commonly used and there is a high chance that aggregating will conflict existing metrics from other jobs in prometheus.

[gontarzpawel]

Hello @bzon, I agree with your proposal. Would you mind submitting a PR?

[mga-chka]

the current PR https://github.com/ContentSquare/chproxy/pull/221 is linked to this topic

[mga-chka]

I'm closing this issue since a namespace was added in https://github.com/ContentSquare/chproxy/pull/221