RFE: Expose DNS prober metrics for the queried name and query type

[siebenmann]

Today it is troublesome to use Blackbox to monitor a bunch of DNS names that you want to check always resolve and alert if they fail, because there is a lot of repetition and duplication needed (multiple Blackbox modules, multiple Prometheus scrape configurations, even multiple alerts). One of the troublesome areas is that if you want to put details about what DNS name and query type in your alert messages, you don't have this information available as labels on the DNS probe metrics from Blackbox and have to source them from elsewhere (separate alerts for each module, magic knowledge of how your DNS module names are formatted so you can split them, add labels to the scrape configurations, there are various ugly options). To help this situation, Blackbox could easily expose an info metric that had this information in labels; you could then use standard PromQL mechanisms to pull this information into your alerts.