br: expose pod metrics to grafana

[BornChanger]

Feature Request

Is your feature request related to a problem? Please describe:

One-time tasks like br， lightning, etc don't expose metrics to grafana. It brings challenge to trouble shooting.

Describe the feature you'd like:

Expose task pod metrics to grafana via push gateway.

Describe alternatives you've considered:

Teachability, Documentation, Adoption, Migration Strategy: