MEDIUM: resolvers: No longer store query items in a list into the response

MEDIUM: resolvers: No longer store query items in a list into the response

When the response is parsed, query items are stored in a list, attached to
the parsed response (resolve_response).

First, there is one and only one query sent at a time. Thus, there is no
reason to use a list. There is a test to be sure there is only one query
item in the response. Then, the reference on this query item is only used to
validate the domain name is the one requested. So the query list can be
removed. We only expect one query item, no reason to loop on query records.
In addition, the query domain name is now immediately checked against the
resolution domain name. This way, the query item is only manipulated during
the response parsing.