Metrics publishing

[brayniac]

Add push support for telemetry publishing, currently we only support pull-based collection. We should extend the metrics library to allow for pluggable exposition and publishing. Targets to consider for push support are InfluxDB and Kafka

[gavmckee80]

@brayniac , having a GNMI server would be amazing , or if not at least the ability to push into Influx 2.x

[brayniac]

@gavmckee80 - push is currently a very low priority for my use-cases. We've found that Rezolus primarily shines as a sampler and that we can leave the ingestion and metrics pipeline to other software.

That said, I'd welcome a PR that adds the ability to push to Influx as long as it can be done in a general fashion and doesn't pull in much else in terms of dependencies. It looks like GNMI involves GRPC, which if I'm not mistaken will involve many additional dependencies.