Async DNS pipeline (trust-dns 0.23)

[valeriansaliou]

No description provided.

[valeriansaliou]

OK, I got everything to a working state, it compiles with no warnings and with full equivalent functionality.

Checklist for what remains:

• Perform further tests (test all cases, or write automated tests)
• Update Trust to Hickory DNS
• Upgrade trust_dns_resolver from 0.10 to 0.23
• Identify synchronous code sections (Redis is one for sure, but there might be other synchronous code paths)

[paulocoghi]

Thanks a lot @valeriansaliou!