[stable/prometheus-postgres-exporter] Add better support for ServiceMonitor targetlabels

[Aaron-ML]

Is your feature request related to a problem? Please describe.
Need to add targetlabels to allow pod / service labels to propagate into prometheus

Describe the solution you'd like
Mirror prometheus-mysql-exporter targetLabel values #15349

Describe alternatives you've considered
Could inject on prometheus level, but you lose flexibility

Additional context
Add any other context or screenshots about the feature request here.

[stale]

This issue has been automatically marked as stale because it has not had recent activity. It will be closed if no further activity occurs. Any further update will cause the issue/pull request to no longer be considered stale. Thank you for your contributions.

[stale]

This issue is being automatically closed due to inactivity.