rec: Reuse the outgoing query protobuf for the incoming response

[rgacogne]

Short description

Allocating memory for the ProtoBuf objects an their fields is costly, as is converting the qname and potential UUID to strings, for example.

Checklist

I have:

• read the CONTRIBUTING.md document
• compiled this code
• tested this code
• included documentation (including possible behaviour changes)
• documented the code
• added or modified regression test(s)
• added or modified unit test(s)

[rgacogne]

CircleCI failure seems unrelated, probably #7899 ?

[Habbie]

CircleCI failure seems unrelated, probably #7899 ?

yes

[omoerbeek]

Only logging answers an no replies is not possible.

It can be a good thing to de-couple this and be able to only log one of the two. As the reply contains the request data the former is enough in some scenarios.

(The dnstap code allows switching on an off for queries and replies independently).

[rgacogne]

Only logging answers an no replies is not possible.

I noticed that as well and was a bit surprised about it because we do support it for the logging of incoming queries and outgoing responses, but I considered it was out of scope for this PR.