add prometheus metrics server and config

[jchappelow]

I want to play with prometheus a bit before saying this is right, but it addresses exposing cometbft's metrics as in #995 (comment)

Prometheus server + Grafana can talk to this and see cometbft's metrics, so I think this is properly exposing CometBFT's metrics endpoint.

Metrics: https://docs.cometbft.com/v0.38/core/metrics

prometheus config

global:
  scrape_interval: 15s # Set the scrape interval to every 15 seconds. Default is every 1 minute.
  evaluation_interval: 15s # Evaluate rules every 15 seconds. The default is every 1 minute.
  # scrape_timeout is set to the global default (10s).

# Alertmanager configuration
alerting:
  alertmanagers:
    - static_configs:
        - targets:
          # - alertmanager:9093

# Load rules once and periodically evaluate them according to the global 'evaluation_interval'.
rule_files:
  # - "first_rules.yml"
  # - "second_rules.yml"

# A scrape configuration containing exactly one endpoint to scrape:
# Here it's Prometheus itself.
scrape_configs:
  # The job name is added as a label `job=<job_name>` to any timeseries scraped from this config.
  - job_name: "prometheus"

    # metrics_path defaults to '/metrics'
    # scheme defaults to 'http'.

    scrape_interval: 5s

    static_configs:
      - targets: ['localhost:26660']

[jchappelow]

Here's some PoC stuff. I marked this counter-type metric as unstable as we should fully specify all of kwild's metrics and organize them better within a hierarchy of namespaces.

[brennanjl]

LGTM, thanks a ton for doing this