Validate domain availability in many ways

Currently, the `DeadDomainsLinter` only checks the exact domain for A record, but:

- An entry `||example.com` might be added by a filter because it might want to block any subdomains, no matter whether the apex domain is reachable or not.
- A domain might only support IPv6 (e.g., `||ipv6.ipcheck.example.com` might be blocked even if it has no A record).

I propose adding extra checks:

- Search for both A and AAAA records
- Use [`tldts`](https://github.com/remusao/tldts) library to get the "registerable" part of the domain (extracting `example.com` from `||blocked.example.com`， `github.io` from `||example.github.io`), check its NS records and whois.
- If an apex domain doesn't have NS records, the answers should only contain SOA records
- Do notice that some authoritative DNS servers don't implement NS records properly (e.g. `qq.com`), that's why we need to check the domain's whois as well.
- Only all the above check fails, we can identify that an entry contains the dead domain.