Which libraries generate observability metrics for applications in the cluster to prometheus?
For Application specific calls you need to use a Prometheus client and create the metrics yourself. The Prometheus client will allow you to create a /metrics endpoint where you can output the current metric values which Prometheus will scrape.

For metrics that are not unique to your application, you can use Prometheus exporters that will run on either the node, container, or runtime environment, or third-party software. These will also create targets which you can tell Prometheus to scrape to gather the metric data.

Once the metric data is collected you'll need to write your own RED and USE queries in graphana to display those metrics.