Merge branch 'zone-events-queue' into opt-refactor

src/knot/server/net.c

src/knot/server/server.c

src/knot/server/udp-handler.c

src/knot/worker/pool.c

src/knot/worker/pool.h

src/knot/zone/events.c

src/knot/zone/events.h

src/knot/zone/zonedb-load.c

src/utils/dig/dig_exec.c