AlgoScan

Existing tests mocked the queryServerIf transport, leaving qsi.queryServer -
the real UDP/TCP behavior - uncovered. Add tests against a loopback DNS
server for: retrying over TCP after a UDP error, retrying over TCP on a
truncated UDP response, advertising the 1232-byte EDNS0 buffer, and
surfacing the per-server error when all attempts fail.

Relay SRV resolution failures were logged only on testnet and devnet; on
mainnet the error was dropped and the only trace was an INFO "got no relay
DNS addrs" line. A mainnet node that resolves no relays then runs with an
empty phonebook, connects to zero peers, and reports itself caught up at a
stale round, with no warning an operator can act on.

Log the relay resolution error as a warning on every network and raise the
empty-relay case to a WARN stating the operational impact. Archive lookups
stay informational, since archival peers are optional for most nodes.

When a query failed against every configured server, query() discarded each
server's error and returned only "no answer for (name, type) from DNS
servers [...]", which is indistinguishable from a missing record. The cause
(timeout, truncation, blocked TCP, ...) was lost, leaving operators with a
lookup that fails here while dig resolves it and nothing to act on.

Join the per-server errors onto the returned error so the real cause is
visible.