Instrument Metrics for Prometheus

[zach-robinson-dev]

The kubert-prometheus-tokio crate should be used to expose runtime metrics to be available for Prometheus. Tokio tasks spawned by Sinker should be instrumented and metrics tracking the status of each ResourceSync should also be added.

[lukebond]

here are the kube-rs docs on observability, with some good examples of how to do it: https://kube.rs/controllers/observability/

[lukebond]

possible duplicate of influxdata/tubernetes#2209