Add support for push-based OLTP transport #104
Description
The Strimzi Metrics Reporter currently supports pull metrics based on the Prometheus format. However, the trends seem to be moving towards OLTP based push metrics when the metrics reporter would push the metrics to the remote monitoring server. We should add support for it to the Strimzi Metrics reporter as well. (While there is support for OLTP metrics in the Prometheus JMX Exporter that can serve as an alternative, I think supporting push metrics in the Strimzi Metrics reporter here would make sure it remains future proof and might help to convince people to use it instead of the Prometheus JMX Exporter.