[Feature]: Grafana dashboard for pooler pgbouncer

### Is there an existing issue already for this feature request/idea?

- [X] I have searched for an existing issue, and could not find anything. I believe this is a new feature request to be evaluated.

### What problem is this feature going to solve? Why should it be added?

It would be nice to have graphs for the bgbouncer. Metrics are available ( "cnpg_pgbouncer_*" ) .
Since CNPG easily provides postgres with pgbouncer I think it would be great to also have the dashboard for the pooler
which uses the cnpg metrics.
It's becoming more often, that poolers are requested in addition to a cnpg cluster, and therefore a dashboard helps to monitor and make adjustments.

### Describe the solution you'd like

I found dashboards on grafanas website, which would describe the solution best.
https://grafana.com/grafana/dashboards/9760-postgresql-pgbouncer/
https://grafana.com/grafana/dashboards/14022-pgbouncer/

But these are not well maintained. Also the expected names for metrics don't match with cnpg exported metrics - expected naming is that of pgbouncer exporter.

### Describe alternatives you've considered

The only alternative I see is taking a dashboard from grafana myself and try to make it work with the metrics exported by cnpg.

### Additional context

_No response_

### Backport?

N/A

### Are you willing to actively contribute to this feature?

No

### Code of Conduct

- [X] I agree to follow this project's Code of Conduct