resolved: replace "answer_authenticated" bool by uint64_t query_flags field

resolved: replace "answer_authenticated" bool by uint64_t query_flags field

Let's use the same flags type we use for client communication, i.e.
instead of "bool answer_authenticated", let's use "uint64_t
answer_query_flags", with the SD_RESOLVED_AUTHENTICATED flag.

This is mostly just search/replace, i.e. a refactoring, no change in
behaviour.

This becomes useful once in a later commit SD_RESOLVED_CONFIDENTIAL is
added to indicate resolution that either were encrypted (DNS-over-TLS)
or never left the local system.