[Enhancement][opensearch/opensearch-dashboards] ServiceMonitor is missing the ability to add a specific label to it

[eyenx]

Is your feature request related to a problem? Please describe. When enabling ServiceMonitor one might need to add a specific label to it to make it scrapable by Prometheus

Describe the solution you'd like Additional serviceMonitor.selector value or extraLabels to add to the serviceMonitor

Describe alternatives you've considered Just adding labels to the global labels value. But this would end up in the deployments and other resources as well.

Additional context I will open up a PR myself.