Collect metrics from warp tunnels

[ntfrnzn]

Add additional metrics from the ingress controller itself.

[ntfrnzn]

https://github.com/cloudflare/cloudflare-ingress-controller/commit/645b3c21b03217d827a5400a594a9553f1386b77 begins to expose the metrics that already exists. But there are a few problems inherent with the cloudflared library,

• the gauges and counters are all registered with the static DefaultRegisterer which makes things tricky for testing at least
• the metrics are shared across all tunnels/ingresses, and there's no label per ingress

A particular ingress controller that exposes more than one service, at more than one hostname, will be reporting metrics that aggregate across all tunnels/ingresses/services.

There's no way around this without reworking the metrics in the cloudflared library, and even then it may require things like custom collecters to aggregate metric per-ingress or per-tunnel.