libknot/rdataset: rename structure items

src/knot/ctl/commands.c

src/knot/dnssec/ds_query.c

src/knot/dnssec/nsec3-chain.c

src/knot/dnssec/rrset-sign.c

src/knot/dnssec/zone-nsec.c

src/knot/dnssec/zone-sign.c

src/knot/events/handlers/refresh.c

src/knot/journal/serialization.c

src/knot/nameserver/process_query.c

src/knot/updates/apply.c

src/knot/updates/ddns.c

src/knot/zone/contents.c

src/knot/zone/node.c

src/knot/zone/semantic-check.c

src/knot/zone/zone-diff.c

src/knot/zone/zone-dump.c

src/knot/zone/zonefile.c

src/libknot/packet/pkt.c

src/libknot/packet/rrset-wire.c

src/libknot/rdataset.c