dns server answers any incoming message as if it were a query

i noticed this while looking at an implementation supporting ServerFuture... conspicuously, we do not check the request was a Query (or, surprise to me: a Query can have Opcode::Update?!) in our roughly-analogous code.

as a validation, i adjusted this test helper from #6308 away from trust_client.query, to trust_client.notify(name, DNSClass:IN, RecordType::AAAA, None::<trust_dns_proot::rr::RecordSet>) instead. this has the client send a nonsense NOTIFY for an AAAA record which if faithfully interpreted probably should tell the server that the record should be refreshed from whoever is authoritative for the name. instead, we return the AAAA record as if it was a query, and the test still passes!

much like the implementation in hickory-dns, we ought to only be answering queries, and least logging or ignoring requests with parameters we don't know.

Start in dns-server/src/dns_server.rs around the roughly analogous request handling at lines 260-270, then inspect the test helper changed in PR #6308. Use trust_client.notify with the existing test setup to cover a non-query request. Done means the DNS server answers queries only and logs or ignores requests with unsupported parameters.