Optimized probe listing endpoints

[jimaek]

We need:

• A way to show thousands of probes on the map, both as complete picture and results after the test
• Totals. How many probes, in how many cities, countries, ASNs, ISPs. To say for example "We have 4000 probes in 300 countries, in 600 cities, covering 1000 ASNs hosted with 800 ISPs". It will be used on different pages of the site and maybe CLI
• Reverse totals. How many probes per city, country, ASN, ISP.... To say "We have 400 probes in USA, 200 in Europe, 100 with ASN 599..."
• A list of countries, ISPs, ASNs... with at least 1 probe in them. Mostly needed for new web tools