Resolve !1509 with 6.0 (libknot 3.4 compatibility)

Resolve !1509 with 6.0 (libknot 3.4 compatibility)

- some knot_wire_next_label() calls were added since master,
  so those get changed as in a083f3fe63cffbabb19e6b67848151f4bb6d623c
- some code has moved since master (to lib/resolve-produce.c),
  and unfortunately the MR !1509 did change some of it,
  and git was unable to handle this automatically

This merge commit is separate, only bringing !1509 and no other
changes from master, so that it's easier to understand.