libknot: add basic support for SVCB and HTTPS records
- They were registered by IANA some time ago: https://www.iana.org/assignments/dns-parameters/dns-parameters.xhtml
- They now appear in traffic quite a lot and I'm getting tired of TYPE65 in logs :-)
- I don't expect a more precise descriptor is wanted, when comparing to other types. Wire-format reference: https://mikebishop.github.io/dns-alt-svc/draft-ietf-dnsop-svcb-https.html#name-rdata-wire-format
- No displaying or parsing, for now. (except for displaying the type names)