bug: all "Unstoppable Domains" (.crypto) DoH resolvers are down

[lidel]

This is similar to #771 but at the time of writing this all UD DoH resolvers seem to be down, breaking DNSLink websites loaded via boxo/gateway if the domain name uses the .crypto TLD.

Current implicit default is Cloudflare at https://resolver.cloudflare-eth.com/dns-query and it stopped returning DNSLink results earlier today (filled support ticket to CF).

The "official" DoH at https://resolver.unstoppable.io/dns-query just hangs and timeouts.

I guess we wait for Cloudflare fix, but if that does not start working we need to consider altenatives (are there any? removal?)

[lidel]

Friendly ping to https://github.com/orgs/unstoppabledomains/people: @nickshatilo @bonsaiben

How does DoH story look like for UD? Should we keep defaulting to Cloudflare (assuming its fixed soon)?
We would prefer using https://resolver.unstoppable.io/dns-query directly, but it seems to be offline.

I'm testing with:

$ curl 'https://resolver.unstoppable.io/dns-query?name=_dnslink.test.crypto&type=TXT' -H 'accept: application/dns-json' -v
* Host resolver.unstoppable.io:443 was resolved.
* IPv6: (none)
* IPv4: 3.33.139.32
*   Trying 3.33.139.32:443...
* ALPN: curl offers h2,http/1.1
* TLSv1.3 (OUT), TLS handshake, Client hello (1):

and just hangs.

Team is on holiday, but we would like to resolve this in January (either fix .crypto, or remove default resolver.cloudflare-eth.com if not fixed by then)