Expand valid/invalid tests to check v4/v6 separately

[mahtin]

It would be nice to show the valid/invalid URL fetch results with v4 and v6 answers separated. Mainly to confirm both are working or not working. Of course this could also show that no v6 is seen by the browser - which is not the point of this site.

[fuero]

And it would prevent false positives if people are forced to use a tunnel broker for v6.

[ardje]

I got a false positive on xs4all that is my main v6 provider, because it falls back to v4 and uses my primary v4 provider tweak. By hand xs4all tests 100% clear (which I expected them to).
wget -4qO - https://valid.rpki.cloudflare.com
{"status":"valid", "asn":25596, "name": "Cambrium BV."}
wget -6qO - https://valid.rpki.cloudflare.com
{"status":"valid", "asn":3265, "name": "XS4ALL Internet B.V."}
So having a {in,}valid-v{4,6} would be nice.