Support prometheus push metrics

[siladu]

Add configuration for and pass through to Besu library, tested with Besu's instructions https://besu.hyperledger.org/en/stable/public-networks/how-to/monitor/metrics/#run-prometheus-with-besu-in-push-mode

Example CLI Usage:

web3signer --metrics-push-enabled --metrics-push-port 9091 --metrics-push-host=127.0.0.1  \
--metrics-push-interval=30 --metrics-push-prometheus-job="web3signer-job" \
eth2 --slashing-protection-enabled=false

Example config.yaml Usage web3signer --config-file=config.yaml eth2:

metrics-push-enabled: true
metrics-push-port: 9091
metrics-push-host: 127.0.0.1
metrics-push-interval: 60
metrics-push-prometheus-job: "web3signer-job"

eth2.slashing-protection-enabled: false

Minimal Usage (using defaults):

web3signer --metrics-push-enabled eth2 --slashing-protection-enabled=false

Defaults:

--metrics-push-enabled Enable the metrics push gateway integration
                               (default: false)
--metrics-push-host=<HOST>
                             Host of the Prometheus Push Gateway for push mode
                               (default: 127.0.0.1)
--metrics-push-port=<PORT>
                             Port of the Prometheus Push Gateway for push mode
                               (default: 9001)
--metrics-push-interval=<INTEGER>
                             Interval in seconds to push metrics when in push
                               mode (default: 15)
--metrics-push-prometheus-job=<metricsPrometheusJob>
                             Job name to use when in push mode (default:
                               web3signer-job)

Fixed Issue(s)

Fixes #790

Documentation

• I thought about documentation and added the doc-change-required label to this PR if updates are required.

Changelog

• I thought about adding a changelog entry, and added one if I deemed necessary.

[usmansaleem]

LGTM

[usmansaleem]

LGTM - minor comment around checking for null.

[bgravenorst]

Removing label because this issue is now in the Doc backlog.