Add & fix helm metrics endpoint

[kwongtn]

The existing declaration does not expose the deployment to collect metrics from the pods, hence no metrics are being collected.

This PR exposes the metrics port, and also includes a "for-convenience" PodMonitor. As some of us may already have metrics setup, I bumped the semver by 1 minor version to prevent anyone accidentally updating & wiping their configs.

Closes #871

Depends on:

• https://github.com/postgresml/pgcat/pull/890

[tomasz-torcz-airspace-intelligence]

Could you also add pod annotation for classic Prometheus deployments?

metadata:
  annotations:
    prometheus.io/port: "9930"
    prometheus.io/scrape: "true"

[shigedangao]

any update @kwongtn ?